Update package / docker versions and cleanup

frontend/Dockerfile

-FROM node:12
+FROM node:15.13.0-alpine3.13
 
 WORKDIR /usr/src/app
 

frontend/package.json

@@ -3,7 +3,6 @@
   "version": "0.1.0",
   "private": true,
   "dependencies": {
-    "@ffmpeg/core": "^0.8.5",
     "@ffmpeg/ffmpeg": "^0.9.6",
     "@giantmachines/redux-websocket": "^1.4.0",
     "@material-ui/core": "^4.11.0",
@@ -14,19 +13,15 @@
     "@testing-library/user-event": "^12.1.10",
     "@types/ffmpeg.js": "^3.1.1",
     "@types/react-redux": "^7.1.11",
-    "ffmpeg.js": "^4.2.9003",
-    "memfs": "^3.2.0",
     "react": "^17.0.1",
     "react-dom": "^17.0.1",
     "react-player": "^2.7.0",
     "react-redux": "^7.2.2",
-    "react-scripts": "4.0.0",
+    "react-scripts": "^4.0.0",
     "redux": "^4.0.5",
-    "redux-loop": "^6.0.1",
     "redux-saga": "^1.1.3",
-    "redux-thunk": "^2.3.0",
     "styled-components": "^5.2.1",
-    "typescript": "4.0.5",
+    "typescript": "^4.0.5",
     "web-vitals": "^0.2.4"
   },
   "scripts": {

frontend/src/backendconnection/communication.ts

@@ -84,7 +84,7 @@ function* fetchUser(action: any) {
         break;
       }
       case "get-playback-time": {
-        let playtime = yield select(selectSeconds);
+        let playtime: number = yield select(selectSeconds);
         console.log(playtime);
         yield put(sendPlayerTime(playtime));
         break;
@@ -113,7 +113,7 @@ function* handleConnectionStatus(action: any) {
       break;
     }
     case "REDUX_WEBSOCKET::CLOSED": {
-      let isConnect = yield select(selectConnected);
+      let isConnect: boolean | null = yield select(selectConnected);
       if (isConnect !== null) {
         yield put(setConnectionStatus(false));
       }