Add support for JSON-formatted tiddler store, and make it the default (#5708)

* Add support for JSON-formatted tiddler store, and make it the default

The change to `getTiddlersAsJson()` is to allow experimentation

* Move JSON tiddlers into their own store area, and fix support for encrypted tiddlers

Also add a dummy old-style store area for backwards compatibility

The current arrangement is that JSON tiddlers will always override old-style tiddlers.

* Use the deserialiser mechanism to decode the content

* Refactor $:/core/modules/deserializers.js before we start extending it

Cleaning up the helper function names and ordering

* Drop support for the "systemArea" div

It was only used in really old v5.0.x

* Update deserializer to support JSON store format and add some tests

* Life UI restrictions on characters in fieldnames

* Add another test case

* Correct mis-merge

* Remove toLowerCase() methods applied to fieldnames

* Insert line breaks in output of getTiddlersAsJson (#5786)

Rather than have the entire store on one line, insert a line break
after each tiddler.

* Refactor #5786 for backwards compatibility

* Only read .tiddlywiki-tiddler-store blocks from script tags

Prompted by @simonbaird's comment here: https://github.com/Jermolene/TiddlyWiki5/pull/5708#discussion_r648833367

* Clean up escaping of unsafe script characters

It seems that escaping `<` is sufficient

* Add docs from @saqimtiaz

Thanks @saqimtiaz

* Docs tweaks

* Remove excess whitespace

Thanks @simonbaird

* Fix templates for lazy loading

* Remove obsolete item from release note

* Clean up whitespace

* Docs for the jsontiddler widget

* Fix whitespace

Fixes #5840

* Comments

* Fix newlines in JSON store area

* Remove obsolete docs change

Co-authored-by: Simon Baird <simon.baird@gmail.com>

languages/ru-RU/Misc.multids

@@ -19,7 +19,6 @@ Encryption/PromptSetPassword: Установить новый пароль дл
 Encryption/RepeatPassword: Повторите пароль
 Encryption/SetPassword: Введите пароль
 Encryption/Username: Имя пользователя
-InvalidFieldName: Недопустимые символы в названии поля "<$text text=<<fieldName>>/>". Поля могут содержать только латинские буквы нижнего регистра, цифры и символы: подчеркивание (`_`), дефис (`-`) и точку (`.`)
 MissingTiddler/Hint: Заметка "<$text text=<<currentTiddler>>/>" отсутствует - нажмите {{||$:/core/ui/Buttons/edit}} чтобы её создать
 OfficialPluginLibrary: Официальная Библиотека Плагинов ~TiddlyWiki
 PluginReloadWarning: Пожалуйста, сохраните {{$:/core/ui/Buttons/save-wiki}} и перезапустите {{$:/core/ui/Buttons/refresh}} вики, чтобы изменения в плагинах возымели эффект.