add section for testers in about page

locales/en-US.yml

@@ -1844,6 +1844,7 @@ _aboutMisskey:
   morePatrons: "We also appreciate the support of many other helpers not listed here. Thank you! 🥰"
   patrons: "Patrons"
   projectMembers: "Project members"
+  testers: "Testers"
 _displayOfSensitiveMedia:
   respect: "Hide media marked as sensitive"
   ignore: "Display media marked as sensitive"

locales/index.d.ts

@@ -7164,6 +7164,10 @@ export interface Locale extends ILocale {
          * プロジェクトメンバー
          */
         "projectMembers": string;
+        /**
+         * テスター
+         */
+        "testers": string;
     };
     "_displayOfSensitiveMedia": {
         /**

locales/ja-JP.yml

@@ -1866,6 +1866,7 @@ _aboutMisskey:
   morePatrons: "他にも多くの方が支援してくれています。ありがとうございます🥰"
   patrons: "支援者"
   projectMembers: "プロジェクトメンバー"
+  testers: "テスター"
 
 _displayOfSensitiveMedia:
   respect: "センシティブ設定されたメディアを隠す"