update vuepress dependencies

{

  "devDependencies": {

    "@vuepress/plugin-docsearch": "2.0.0-beta.29",

    "@vuepress/plugin-git": "2.0.0-beta.29",

    "@vuepress/plugin-google-analytics": "2.0.0-beta.29",

    "@vuepress/plugin-medium-zoom": "2.0.0-beta.29",

    "@vuepress/plugin-nprogress": "2.0.0-beta.29",

    "@vuepress/plugin-pwa": "2.0.0-beta.29",

    "@vuepress/plugin-pwa-popup": "2.0.0-beta.29",

    "@vuepress/plugin-register-components": "2.0.0-beta.29",

    "@vuepress/plugin-toc": "2.0.0-beta.29",

    "vuepress": "2.0.0-beta.29"

    "@vuepress/plugin-docsearch": "2.0.0-beta.31",

    "@vuepress/plugin-git": "2.0.0-beta.31",

    "@vuepress/plugin-google-analytics": "2.0.0-beta.31",

    "@vuepress/plugin-medium-zoom": "2.0.0-beta.31",

    "@vuepress/plugin-nprogress": "2.0.0-beta.31",

    "@vuepress/plugin-pwa": "2.0.0-beta.31",

    "@vuepress/plugin-pwa-popup": "2.0.0-beta.31",

    "@vuepress/plugin-register-components": "2.0.0-beta.31",

    "@vuepress/plugin-toc": "2.0.0-beta.31",

    "vuepress": "2.0.0-beta.31"

  },

  "scripts": {

    "docs:dev": "vuepress dev docs",