refactor: GM APIs

src/btn.ts

@@ -2,7 +2,7 @@
 import { ScoreInfo } from './scoreinfo'
 import { loadMscore, WebMscore } from './mscore'
 import { useTimeout, windowOpenAsync, console, attachShadow } from './utils'
-import { isGmAvailable, registerMenuCommand } from './gm'
+import { isGmAvailable, _GM } from './gm'
 import i18n from './i18n'
 // @ts-ignore
 import btnListCss from './btn.css'
@@ -88,8 +88,9 @@ export class BtnList {
     }
 
     // add buttons to the userscript manager menu
-    if (isGmAvailable()) {
-      registerMenuCommand(options.name, () => {
+    if (isGmAvailable('registerMenuCommand')) {
+      // eslint-disable-next-line no-void
+      void _GM.registerMenuCommand(options.name, () => {
         options.action(options.name, btnTpl, () => undefined)
       })
     }

src/gm.ts

@@ -3,17 +3,17 @@
  * UserScript APIs
  */
 declare const GM: {
+  /** https://www.tampermonkey.net/documentation.php#GM_info */
+  info: Record<string, any>;
+
   /** https://www.tampermonkey.net/documentation.php#GM_registerMenuCommand */
   registerMenuCommand (name: string, fn: () => any, accessKey?: string): Promise<number>;
 }
+export const _GM = GM
 
 type GM = typeof GM
 
-export const isGmAvailable = (): boolean => {
+export const isGmAvailable = (requiredMethod: keyof GM = 'info'): boolean => {
   return typeof GM !== 'undefined' &&
-    typeof GM.registerMenuCommand === 'function'
-}
-
-export const registerMenuCommand: GM['registerMenuCommand'] = (...args) => {
-  return GM.registerMenuCommand(...args)
+    typeof GM[requiredMethod] !== 'undefined'
 }