Migrate action, common, a11y translation keys

```
move () {
  FROM=$1 TO=$2 find public/locales -type f -exec sh -c 'jq ".$TO = .\"$FROM\" | del(.\"$FROM\") | del(..|nulls) | select(length > 0)" {} | sponge {}' \;
}

move "Avatar" "common.avatar"
move "Camera" "common.camera"
move "Close" "action.close"
move "Copied!" "common.copied"
move "Copy" "action.copy"
move "Copy link" "action.copy_link"
move "Encrypted" "common.encrypted"
move "Go" "action.go"
move "Home" "common.home"
move "Invite" "action.invite"
move "Loading…" "common.loading"
move "Microphone" "common.microphone"
move "No" "action.no"
move "Not encrypted" "common.unencrypted"
move "Password" "common.password"
move "Profile" "common.profile"
move "Username" "common.username"
move "Video" "common.video"
move "Register" "action.register"
move "Remove" "action.remove"
move "Settings" "common.settings"
move "Sign in" "action.sign_in"
move "Sign out" "action.sign_out"
move "Submit" "action.submit"
move "User menu" "a11y.user_menu"
move "Audio" "common.audio"
move "Display name" "common.display_name"
```

public/locales/ja/app.json

@@ -2,56 +2,62 @@
   "<0>Already have an account?</0><1><0>Log in</0> Or <2>Access as a guest</2></1>": "<0>既にアカウントをお持ちですか？</0><1><0>ログイン</0>または<2>ゲストとしてアクセス</2></1>",
   "<0>Create an account</0> Or <2>Access as a guest</2>": "<0>アカウントを作成</0>または<2>ゲストとしてアクセス</2>",
   "<0>Oops, something's gone wrong.</0>": "<0>何かがうまく行きませんでした。</0>",
-  "Camera": "カメラ",
-  "Avatar": "アバター",
-  "Audio": "音声",
   "Confirm password": "パスワードを確認",
-  "Close": "閉じる",
-  "Copied!": "コピーしました！",
-  "Copy": "コピー",
   "Create account": "アカウントを作成",
-  "Go": "続行",
   "Element Call Home": "Element Call ホーム",
-  "Display name": "表示名",
   "Developer": "開発者",
   "Full screen": "全画面表示",
   "Exit full screen": "全画面表示を終了",
   "Include debug logs": "デバッグログを含める",
-  "Home": "ホーム",
   "Join existing call?": "既存の通話に参加しますか？",
   "Join call now": "今すぐ通話に参加",
   "Join call": "通話に参加",
   "Not registered yet? <2>Create an account</2>": "アカウントがありませんか？ <2>アカウントを作成</2>",
-  "Microphone": "マイク",
   "Login": "ログイン",
   "Logging in…": "ログインしています…",
-  "Loading…": "読み込んでいます…",
   "Version: {{version}}": "バージョン：{{version}}",
-  "Username": "ユーザー名",
-  "User menu": "ユーザーメニュー",
   "Submit feedback": "フィードバックを送信",
   "Spotlight": "スポットライト",
   "Send debug logs": "デバッグログを送信",
-  "Sign out": "サインアウト",
-  "Sign in": "サインイン",
   "Share screen": "画面共有",
-  "Settings": "設定",
   "Sending…": "送信しています…",
   "Sending debug logs…": "デバッグログを送信しています…",
   "Return to home screen": "ホーム画面に戻る",
   "Registering…": "登録しています…",
-  "Register": "登録",
-  "Profile": "プロフィール",
   "Passwords must match": "パスワードが一致する必要があります",
-  "Password": "パスワード",
   "Speaker": "スピーカー",
-  "Video": "ビデオ",
   "Waiting for other participants…": "他の参加者を待機しています…",
   "Yes, join call": "はい、通話に参加",
   "Select an option": "オプションを選択",
   "Debug log request": "デバッグログを要求",
   "Login to your account": "アカウントにログイン",
-  "Remove": "削除",
-  "No": "いいえ",
-  "This call already exists, would you like to join?": "この通話は既に存在します。参加しますか？"
+  "This call already exists, would you like to join?": "この通話は既に存在します。参加しますか？",
+  "common": {
+    "avatar": "アバター",
+    "camera": "カメラ",
+    "copied": "コピーしました！",
+    "home": "ホーム",
+    "loading": "読み込んでいます…",
+    "microphone": "マイク",
+    "password": "パスワード",
+    "profile": "プロフィール",
+    "username": "ユーザー名",
+    "video": "ビデオ",
+    "settings": "設定",
+    "audio": "音声",
+    "display_name": "表示名"
+  },
+  "action": {
+    "close": "閉じる",
+    "copy": "コピー",
+    "go": "続行",
+    "no": "いいえ",
+    "register": "登録",
+    "remove": "削除",
+    "sign_in": "サインイン",
+    "sign_out": "サインアウト"
+  },
+  "a11y": {
+    "user_menu": "ユーザーメニュー"
+  }
 }