fix: some launch review issues

[asjqkkkk]

Fix the issue listed below：

• the slash menu position is incorrect
• The title doesn’t display properly
• the arrow in the menu is not visible on dark mode
• mention page icon is cropped. See: paper clip icon
• table and date or reminder should have no second leven menu
• presses backspace to return first layer
• slash menu reorganization
• add change button for icon uploader
• enable dragging a svg file to upload as icon

Feature Preview

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PR Checklist

• My code adheres to AppFlowy's Conventions
• I've listed at least one issue that this PR fixes in the description above.
• I've added a test(s) to validate changes in this PR, or this PR only contains semantic changes.
• All existing tests are passing.

[github-actions]

🥷 Ninja i18n – 🛎️ Translations need to be updated

Project /project.inlang

lint rule	new reports	level	link
Missing translation	290	warning	contribute (via Fink 🐦)