Element 1.9.4

What's new in this version:

Features:
- Improve the look of tooltips
- Improve the look of the spinner
- Polls: Creation form & start event
- Show a gray shield when encrypted by deleted session
- Make message separator more accessible
- Implement RequiresClient capability for widgets
- Respect the system high contrast setting when using system theme
- Remove redundant duplicate mimetype field which doesn't conform to spec
- Make join button on space hierarchy action in the background
- Add a high contrast theme (a variant of the light theme)
- Improve timeline message for restricted join rule changes
- Improve the appearance of the font size slider
- Improve RovingTabIndex & Room List filtering performance
- Remove outdated Spaces restricted rooms warning
- Make /msg param optional for more flexibility
- Add decoration to space hierarchy for tiles which have already been j…
- Add insert link button to the format bar
- Improve visibility of font size chooser
- Soften border-radius on selected/hovered messages
- Add a developer mode flag and use it for accessing space timelines
- Position toggle switch more clearly
- Validate email address in forgot password dialog nd
- Handle and i18n M_THREEPID_IN_USE during registration
- For space invite previews, use room summary API to get the right member count
- Simplify Space Panel notification badge layout
- Use prettier hsName during 3pid registration where possible

Fixed:
- Add a condition to only activate the resizer which belongs to the clicked handle
- Restore composer focus after event edit
- Don't apply message bubble visual style to media messages
- Handle no selected screen when screen-sharing
- Add history entry before completing emoji
- Add padding between controls on edit form in message bubbles
- Respect the roomState right container request for the Jitsi widget
- Fix cannot read length of undefined for room upgrades
- Cleanup re-dispatching around timelines and composers
- Fix removing a room from a Space and interaction with m.space.parent
- Fix recent css regression
- Fix ModalManager reRender racing with itself
- Fix fullscreening a call while connecting
- Allow scrolling right in reply-quoted code block
- Fix dark theme codeblock colors
- Show passphrase input label
- Always render disabled settings as disabled
- Make "Security Phrase" placeholder look consistent cross-browser
- Fix direction override characters breaking member event text direction
- Remove redundant text in verification dialogs
- Fix space panel name overflowing
- Fix conflicting CSS on syntax highlighted blocks