feat: switch from npm to yarn (#500)

* feat: switch from npm to yarn

* fix: build

* fix: replace yarn run with yarn

* fix: nodejs version install in Docker image

* fix: initialize mobx state

Co-authored-by: Karol Sójko <karolsojko@gmail.com>

app/assets/javascripts/ui_models/app_state.ts

@@ -61,8 +61,8 @@ class ActionsMenuState {
 
 export class SyncState {
   inProgress = false;
-  errorMessage?: string;
-  humanReadablePercentage?: string;
+  errorMessage?: string = undefined;
+  humanReadablePercentage?: string = undefined;
 
   constructor() {
     makeObservable(this, {