feat: add ability to save files

[sehyod]

This adds the ability to save files:

• Files are saved in memory so that switching between tabs does not reset the content
• Pressing cmd+S (or ctrl+S in non-macOS environment) saves the file on the disk
• Saving is also available in the top menu, in File->Save

Screen.Recording.2023-06-27.at.13.06.39.mov

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Implementation choices:
Four atoms are available for files:

• loadableFileAtom is the atom containing the loadable file (the state is loading when initially reading the file from disk, and should stay hasData afterwards)
• updateFileBufferAtom updates a buffer atom. This is currently updated on every update in the editor. The need of a buffer comes from the fact that updating the actual atom triggers a re-render of the editor, that deletes the history and resets focus
• saveFileInMemoryAtom saves the content of the buffer in the loadableFileAtom. This atom is currently called when an editor instance is unmounted (ie. when switching between tabs)
• saveFileAtom actually writes the content of the buffer on the disk. It does NOT update the loadableFileAtom, to prevent the editor from re-rendering and resetting focus and history.

Closes #197

[codecov]

Codecov Report

Merging #204 (e4250db) into main (90949c1) will increase coverage by 0.14%.
The diff coverage is 60.32%.

@@            Coverage Diff             @@
##             main     #204      +/-   ##
==========================================
+ Coverage   71.99%   72.13%   +0.14%     
==========================================
  Files          97       99       +2     
  Lines        4859     4974     +115     
  Branches      391      405      +14     
==========================================
+ Hits         3498     3588      +90     
- Misses       1344     1369      +25     
  Partials       17       17              

Impacted Files	Coverage Δ
src/App.tsx	0.00% <0.00%> (ø)
src/editor/TipTapEditor.tsx	0.00% <0.00%> (ø)
src/panels/MainPanel.tsx	0.00% <0.00%> (ø)
src/views/TipTapView.tsx	0.00% <0.00%> (ø)
src/filesystem.ts	17.68% <12.50%> (-0.30%)	⬇️
src/EventsListener.tsx	100.00% <100.00%> (ø)
src/atoms/core/fileContent.ts	100.00% <100.00%> (ø)
src/atoms/core/paneGroup.ts	100.00% <100.00%> (ø)
src/atoms/createFileContentAtoms.ts	100.00% <100.00%> (ø)
src/atoms/fileActions.ts	100.00% <100.00%> (ø)
... and 3 more

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[danvk]

Exciting that we can persist files now! Two questions:

• Is there a "factory reset" option available? I was playing around with Tiptap and got myself into a bad state. Running yarn tauri:dev:debug no longer resets my state, so I'm not sure how to get out of this.
• When you save a file to disk, where does it go? The refstudio directory?

[sehyod]

• There is no such option for now. However, we are planning on adding the ability to remove files (see Add ability to delete files #212). Could you give more details about the bad state you got yourself into? Maybe it's worth filing an issue about it?
• It goes to the project subdirectory in the refstudio directory. Something like /Users/$USER/Library/Application Support/com.tauri.dev/project-x

[cguedes]

@danvk we've had to update the references model (FE), and since we persist that information in the localStorage sometimes you need to reset that info using the UI (i.e. "DEBUG: reset references store") or directly via dev tools (Application > Storage). I normally also run the ./scripts/reset_uploads.sh utility script to reset all the BE data.