feat: save files as markdown

[sehyod]

Closes #214

This adds an item Save File as Markdown... in the File menu. This opens a dialog to select where to save the file (the default location is an exports directory under the RefStudio project directory). If there are references in the file, this also creates a .bib file with the same name and exports used references in this file.

This also disables default bullet lists and ordered lists because they would not be properly exported. However, this PR also adds a first implementation of bullet list, that should work as expected. order lists will be done in a future PR

[codecov]

Codecov Report

Merging #341 (d1b2c63) into main (e4bcd3e) will decrease coverage by 0.57%.
The diff coverage is 75.79%.

@@            Coverage Diff             @@
##             main     #341      +/-   ##
==========================================
- Coverage   84.94%   84.37%   -0.57%     
==========================================
  Files         153      157       +4     
  Lines        8819     9344     +525     
  Branches      973     1014      +41     
==========================================
+ Hits         7491     7884     +393     
- Misses       1317     1449     +132     
  Partials       11       11              

Files Changed	Coverage Δ
src/application/components/MainPanel.tsx	0.00% <0.00%> (ø)
src/application/views/TextView.tsx	0.00% <0.00%> (ø)
src/features/textEditor/editor/TipTapView.tsx	0.00% <0.00%> (ø)
src/io/filesystem.ts	79.38% <18.66%> (-14.46%)	⬇️
...pTapNodes/notionBlock/commands/toggleBulletList.ts	20.83% <20.83%> (ø)
...Nodes/notionBlock/inputRuleHandlers/dashHandler.ts	31.81% <31.81%> (ø)
...rc/features/textEditor/components/TipTapEditor.tsx	90.38% <60.86%> (-8.42%)	⬇️
...ponents/tipTapNodes/notionBlock/NotionBlockNode.ts	75.49% <91.66%> (+1.32%)	⬆️
...StudioDocument/serialization/MarkdownSerializer.ts	94.36% <94.36%> (ø)
src/atoms/editorActions.ts	97.60% <100.00%> (-0.02%)	⬇️
... and 6 more

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