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"
```

src/home/UnauthenticatedView.tsx

@@ -177,8 +177,8 @@ export const UnauthenticatedView: FC = () => {
               <InputField
                 id="displayName"
                 name="displayName"
-                label={t("Display name")}
-                placeholder={t("Display name")}
+                label={t("common.display_name")}
+                placeholder={t("common.display_name")}
                 type="text"
                 required
                 data-testid="home_displayName"
@@ -209,7 +209,7 @@ export const UnauthenticatedView: FC = () => {
               disabled={loading}
               data-testid="home_go"
             >
-              {loading ? t("Loading…") : t("Go")}
+              {loading ? t("common.loading") : t("action.go")}
             </Button>
             <div id={recaptchaId} />
           </Form>