Fixes 79 typescript errors. Discovered at least two bugs in
`notifications.ts`, and I'm pretty sure this feature was at least
partially broken and may still be, I don't really know how to test it.
After this, only like ~10 typescript errors remain in the codebase but
those are harder to solve.
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Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Fix a regression caused by jQuery removal (`renderPreviewPanelContent`)
And simplify the file editor, it doesn't need to be that complex. And
remove jQuery code.
None of the frontend js/ts files was touched besides these two commands
(edit: no longer true, I touched one file in
61105d0618
because of a deprecation that was not showing before the rename).
`tsc` currently reports 778 errors, so I have disabled it in CI as
planned.
Everything appears to work fine.
