Preparing 3.0.0 release

[vladikoff]

Things to test:

• Add send-to-notes context menu ('Send to Notes' context menu #655)
• Add "Export as HTML" option (Export as HTML #695)
• Use React.js states to render the add-on frontend (Moving code base to React #550)

cc @SoftVision-EmilPasca

[vladikoff]

https://1228-91073350-gh.circle-artifacts.com/0/tmp/circle-artifacts.MicZiHM/firefox_notes-3.0.0.zip

[Natim]

• 698 missing sync tooltip #701
• Add a title attribute to the export as HTML menu item. #702

[sebastienbarbier]

notes_3.0.0rc2.zip

[vladikoff]

Let's add a metrics event for Export to HTML

[vladikoff]

• Content can't be erased from "Notes" after reaching the max line limit #705
• The recently changed headings are not saved, if the sidebar is reopened #711
• Disable the "Sync Your Notes" button while "Syncing changes" status is displayed #708
• No tooltip is displayed when you hover the "Disable Sync" button #707
• Fix border to the right of the sync button... Fix border to the right of the sync button... #718
• Disable 'Send to Notes' context menu item in Notes #714
• The "Disable Sync" and the "Export as HTML" options are wrongly colored in "Dark" theme #715