v0.31.0-beta release

This is a testing release only. Do not use on your production data!

First start may take a long time because of data migration from previous version.

Main focus of this release is search functionality:

• implemented proper fulltext search using Sqlite's FTS5
• exposed "virtual" attributes like isProtected, dateModified etc.
• support for date expressions - e.g. @dateModified>MONTH-1 will get you notes modified in the last month
• we're now storing both local and UTC dates for notes which allows us to make more precise date queries
• redesign of search input and how saved searches are saved.
• saved searches now have refresh button

Other highlights:

• upgrade to CKEditor 12.0.0
• in page search finally works correctly (change to electron-find package)
• context menu "new note" now has submenu which allows specifying note type
• fixes for some note movement/creation edge cases in the note tree (#454) - view only
• Add superscript and subscript support to "Type: Text" #462
• Dark theme table invisible background color #458
• Added CSRF protection #455