projects merge request followups

[nogizhopaboroda]

mr: #124

1. extract EDITOR_DEFAULTS from packages/core/src/components/App.tsx
2. move registerFetcher() out of component scope packages/core/src/components/App.tsx:175
3. find solution to avoid rendering loading screen while switching tabs
4. store history for each file separately packages/core/src/store/history/index.ts:120
5. move currentFileIndex inside project packages/core/src/store/projectStore.ts:13
6. implement unregister fetcher functionality packages/fetch/index.ts:12