Add missing descriptions

| branches[i].ratio         | number |     x    | The weight to randomly distribute enrolled clients among the branches.                                                                          |                                                                |

| match                     | object |     x    | Object containing the filter parameters to match specific user groups.                                                                          |                                                                |

| match.app_id              | regex  |          | The app ID (package name)                                                                                                                       | "^org.mozilla.firefox_beta${'$'}|^org.mozilla.firefox${'$'}" |

| match.device_manufacturer | regex  |          |                                                                                                                                                 |                                                                |

| match.device_model        | regex  |          |                                                                                                                                                 |                                                                |

| match.locale_country      |        |          |                                                                                                                                                 | "USA|DEU"                                                    |

| match.locale_language     |        |          |                                                                                                                                                 | "eng|zho|deu"                                                |

| match.app_display_version |        |          |                                                                                                                                                 |                                                                |

| match.device_manufacturer | regex  |          | The Android device manufacturer.                                                                                                                                             |                                                                |

| match.device_model        | regex  |          | The Android device model.                                                                                                                                                |                                                                |

| match.locale_country      |        |          | The default locales country.                                                                                                                                                | "USA|DEU"                                                    |

| match.locale_language     |        |          | The default locales language.                                                                                                                                                | "eng|zho|deu"                                                |

| match.app_display_version |        |          | The application version.                                                                                                                                                |                                                                |

| match.regions             | array  |          | Array of strings. Not currently supported. Custom regions, different from the one from the default locale (like a GeoIP, or something similar). | `["USA", "GBR"]`                                               |

| match.debug_tags          | array  |          | Array of strings. Debug tags to match only specific client for QA of experiments launch & targeting.                                            | `["john-test-1"]`                                              |