add documentation for the 'chart/grid' element

name: chart/grid

desc: |

  The `chart/grid` element is used to draw a background grid.

reference: |

  (chart/grid <options>)

option_summary: true

properties:

  - title: "Grid Options"

    anchor: grid-options

    properties:

      - name: ticks-x

        desc: |

          The 'ticks-x' option controls the x grid placement.

        desc_code: |

          ticks <ticks>

        examples: |

          ;; subdivide the axis with 10 ticks

      - name: ticks-y

        desc: |

          The 'ticks-y' option controls the y grid placement.

        desc_code: |

          ticks <ticks>

        examples: |

          ;; subdivide the axis with 10 ticks

      - name: stroke

        desc: |

          Set the grids's stroke style. See the

          [stroke-style](#FIXME) page for more details on valid values.

        desc_code: |

          stroke (<stroke-style>)

        examples: |

          ;; set the stroke to 2px solid

          stroke (2px solid)

      - name: color

        desc: |

          Set the grids's color. See the

          [color](#FIXME) page for more details on valid values.

        desc_code: |

          color <color>

        examples: |

          ;; set the color to #333

          color #333

  - title: "Scale Options"

    anchor: scale-options

    inherit: ["elements/chart/layout", "scale-options"]

      -

        title: "chart/points"

        url: "/documentation/elements/chart/points"

      -

        title: "chart/grid"

        url: "/documentation/elements/chart/grid"

  -

    title: "Community"