doc: Update documentations for CMSIS 5.9.0

# CMSIS Version 5

The branch *master* of this GitHub repository contains the CMSIS Version 5.8.0.  The [documentation](http://arm-software.github.io/CMSIS_5/General/html/index.html) is available under http://arm-software.github.io/CMSIS_5/General/html/index.html

[![Version](https://img.shields.io/github/v/release/arm-software/CMSIS_5)](https://github.com/ARM-software/CMSIS_5/releases/latest) [![License](https://img.shields.io/github/license/arm-software/CMSIS_5)](https://arm-software.github.io/CMSIS_5/General/html/LICENSE.txt)

The branch *master* of this GitHub repository contains ![Version](https://img.shields.io/github/v/release/arm-software/CMSIS_5?display_name=release&label=%20&sort=semver).

The [documentation](http://arm-software.github.io/CMSIS_5/General/html/index.html) is available under http://arm-software.github.io/CMSIS_5/General/html/index.html

Use [Issues](https://github.com/ARM-software/CMSIS_5#issues-and-labels) to provide feedback and report problems for CMSIS Version 5.

**Note:** The branch *develop* of this GitHub repository reflects our current state of development and is constantly updated. It gives our users and partners contiguous access to the CMSIS development. It allows you to review the work and provide feedback or create pull requests for contributions.

A [pre-built documentation](http://www.keil.com/pack/doc/CMSIS_Dev/index.html) is updated from time to time, but may be also generated using the instructions under [Generate CMSIS Pack for Release](https://github.com/ARM-software/CMSIS_5#generate-cmsis-pack-for-release).

A [pre-built documentation](https://arm-software.github.io/CMSIS_5/develop/General/html/index.html) is updated from time to time, but may be also generated using the instructions under [Generate CMSIS Pack for Release](https://github.com/ARM-software/CMSIS_5#generate-cmsis-pack-for-release).

## Overview of CMSIS Components

|[NN](http://arm-software.github.io/CMSIS_5/NN/html/index.html)        | All Cortex-M | Collection of efficient neural network kernels developed to maximize the performance and minimize the memory footprint on Cortex-M processor cores.|

|[RTOS v1](http://arm-software.github.io/CMSIS_5/RTOS/html/index.html) | Cortex-M0/M0+/M3/M4/M7 | Common API for real-time operating systems along with a reference implementation based on RTX. It enables software components that can work across multiple RTOS systems.|

|[RTOS v2](http://arm-software.github.io/CMSIS_5/RTOS2/html/index.html)| All Cortex-M, Cortex-A5/A7/A9 | Extends CMSIS-RTOS v1 with Armv8-M support, dynamic object creation, provisions for multi-core systems, binary compatible interface. |

|[Pack](http://arm-software.github.io/CMSIS_5/Pack/html/index.html)    | All Cortex-M, SecurCore, Cortex-A5/A7/A9 | Describes a delivery mechanism for software components, device parameters, and evaluation board support. It simplifies software re-use and product life-cycle management (PLM). |

|[Pack](http://arm-software.github.io/CMSIS_5/Pack/html/index.html)    | All Cortex-M, SecurCore, Cortex-A5/A7/A9 | Describes a delivery mechanism for software components, device parameters, and evaluation board support. It simplifies software re-use and product life-cycle management (PLM). <br/>Is part of the [Open CMSIS Pack project](https://www.open-cmsis-pack.org). |

|[Build](http://arm-software.github.io/CMSIS_5/Build/html/index.html)  | All Cortex-M, SecurCore, Cortex-A5/A7/A9 | A set of tools, software frameworks, and work flows that improve productivity, for example with Continuous Integration (CI) support.<br/>Is replaced with the [CMSIS-Toolbox](https://github.com/Open-CMSIS-Pack/devtools/tree/main/tools). |

|[SVD](http://arm-software.github.io/CMSIS_5/SVD/html/index.html)      | All Cortex-M, SecurCore | Peripheral description of a device that can be used to create peripheral awareness in debuggers or CMSIS-Core header files.|

|[DAP](http://arm-software.github.io/CMSIS_5/DAP/html/index.html)      | All Cortex | Firmware for a debug unit that interfaces to the CoreSight Debug Access Port. |

|[Zone](http://arm-software.github.io/CMSIS_5/Zone/html/index.html)    | All Cortex-M | Defines methods to describe system resources and to partition these resources into multiple projects and execution areas. |

## Generate CMSIS Pack for Release

This GitHub development repository contains already pre-built libraries (stored in Git-LFS) of various software components (DSP, RTOS, RTOS2).

These libraries are validated for release. Git-LFS needs to be installed to retrieve the actual binary files, please see https://git-lfs.github.com/.

This GitHub development repository lacks pre-built libraries of various software components (RTOS, RTOS2).

In order to generate a full pack one needs to have the build environment available to build these libraries.

This causes some sort of inconvenience. Hence the pre-built libraries may be moved out into separate pack(s)

in the future.

To build a complete CMSIS pack for installation the following additional tools are required:

 - **doxygen.exe**    Version: 1.8.6 (Documentation Generator)

- **duplicate** - This issue is already addressed elsewhere, see comment with provided references.

- **Important Information** - We provide essential informations regarding planned or resolved major enhancements.

- **Important Information** - We provide essential information regarding planned or resolved major enhancements.