feat: Add Sync policy

[bsmth]

Description:

Adding Sync

Motivation:

Sync is incoming

For reviewers:

• Check case sensitivity, such as:

Software\Policies\Mozilla\Firefox\Sync\bookmarks
Software\Policies\Mozilla\Firefox\Sync\Bookmarks

See also:

• https://bugzilla.mozilla.org/show_bug.cgi?id=2015810
• https://github.com/mozilla/enterprise-firefox/pull/313/changes#diff-53e9ab73465fad9f328175c11477a4271e6956a01722ec137eee894397604a62R57

[bsmth]

Having valid JSON here feels like a good thing, although this is likely an unrealistic example. Same with others, like:

{
  "policies": {
    "Sync": {
      "Enabled": true,
      "addresses": true,
      "bookmarks": true,
      "history": true,
      "openTabs": true,
      "passwords": true,
      "paymentMethods": true,
      "addons": true,
      "settings": true,
      "Locked": true
    }
  }
}

v

{
  "policies": {
    "Sync": {
      "Enabled": true | false,
      "addresses": true | false,
      "bookmarks": true | false,
      "history": true | false,
      "openTabs": true | false,
      "passwords": true | false,
      "paymentMethods": true | false,
      "addons": true | false,
      "settings": true | false,
      "Locked": true | false
    }
  }
}