add a backup info for the Upgrade tiddler.
Prepare for 5.0.10 release
Fix problem with version checking logic

Previously, importing a plugin with a semantically identical version
number was not rejected. This meant that attempts to import
5.0.9-prerelease wikis into 5.0.9-beta led to a corrupted wiki, with a
beta core and prerelease plugins.
Refactor utilities out of HTML parser

Some of the functions are useful general purpose parser helpers.
Added wikitext image support

We’ve added a parser to recognise the `[img[URL or tiddler title]]`
format, and an associated image widget.
Typo fix
Start release note for 5.0.10
Fix issues with tiddlers with null fields

Fixing #567
Fix html parser tests
Docs update
Fix incorrect background colour for sidebar tag pills

Fixes #568.
Fix regression with untagged filter operator

Restored previous behaviour of considering a missing tiddler to be
untagged.
Merge pull request #562 from pmario/upgrade-backup-info

add a backup info for the Upgrade tiddler.
Revise warning about backing up before upgrading
Support the image widget in markdown
Update print stylesheet to hide topbar
Use localCompare for sorting strings

So that accented characters get sorted correctly. Or at least as
correctly as browsers allow.
Correct typos in 5.0.9 release note
Add path conversions from TiddlyWiki Classic

TiddlyWiki Classic converts local file URIs to various local native
formats. The same conversions are now performed by the TiddlyFox
adaptor for TW5.
Fix problem with sorting date fields

Introduced a couple of commits ago when the localeCompare() stuff was
added.