Release notes for 0.18.x hotfix

[alexwykoff]

Release Notes:

• Tab previews: stick to changing properties that can be handled by the compositor alone. (#10291)
• Findbar slowness (cmd + F, typing). (#10271)
• Upgrade to muon 4.3.9. (#10262)
• Upgrade to Chromium 60.0.3112.90. (#10261)
• Optimization Opportunities in extensionState. (#10235)
• Extension Popup Not Showing. (#10224)
• Linux rpm is not signed. (#10188)
• Pinned tab will not display. (#10122)
• Cursor not shown when editing a bookmark. (#10104)
• Optimized window initialization data to use shared memory. (#10018)
• About favicons are taking up way too much space in the session store. (#10000)
• Bitwarden widget not shown on webpages, shows only on about pages. (#9437)
• Opening URL from external application (Thunderbird/LibreOffice) does not work any more. (#9193)
• Unhide bitwarden password manager. (#7921)
• Added Bitwarden Password Manager. (#4776)

[luixxiul]

@alexwykoff the last two should be omitted.

[bsclifton]

We do want to keep #4776, but we should hide #7921 because it's basically a duplicate. I updated the labels accordingly 😄

[luixxiul]

@bsclifton thanks!

edit: I've confused bitwarden with enpass, which is also a password manager.