docs: Update docs for new global hotkeys

[caitlinwheeless]

Account page

• Added a hotkeys section

Labeling

• Removed hotkey docs from the Labeling page and placed them in a subpage
• Removed the tables, because they are too difficult to keep in sync with the app
• Added a screenshot instead
• Fleshed out the Shortcut tag section
• Added link to account page section

Docs for #7784

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