Update CodeMirror Documentation

I wish I could have added tiddlers to the documentation in order to put the mini-tutorials in tabs but I couldn't.
So it is a bit messy in my opinion, but I think it is a good start.

I have tested every configuration with Tiddlywiki v 5.1.4.
Doc: How to Add A Menu to the Sidebar

This item is tagged so as to appear under Customise TiddlyWiki.
Transcluding information re Sidebar Menus

Transcluding information from newly proposed tiddler "How to Add A Menu to the Sidebar". This should help users discover ways in which to use the TOC macro.
new buttons, exporter texts
Add hooks mechanism and th-opening-default-tiddlers-list hook

see: https://github.com/Jermolene/TiddlyWiki5/issues/1064
add /dev docs
Remove alert from addHook.

Thanks to @tobibeer
Improve compatibility with JS modules

If a module ended with a single line comment `\\` then the appended
`;})();` was being ignored and eaten up as part of the comment.
Merge pull request #1101 from pmario/german-translation

German translation updates: new buttons, exporter texts
Fix advanced filter search clear button

Thanks @BramChen
Tweak close button in advanced search
fixed toolbar button spacing

* removed trailing whitespaces in button tids
* defined a global left margin for buttons set to 5px
* slightly less than in view-mode before
* slightly more than in edit-mode before
* but visually more appealing to me
* leaves a wee more room for the title to unfold
Use the fr-FR translated Contribution banner in observance of 86329835c91cdad24b214ea09649dc9573f90cf6
Pointer to the fr-FR edition
put notifications above topbar
Docs tweaks
Add @tobibeer's TB5 resource
Merge pull request #1127 from tobibeer/fix-notification-z-index

put tc-notification above topbar
Merge pull request #1126 from xcazin/fred

Tweaks related to the fr-FR edition
Clean up github contribution banner

Sorry @xcazin I think you may need to do some clearing up after this