Optionally allow click outside to close modals (#7072)

* feat: option to allow click on modalBackdrop to close modal

* feat: allow switcher modals closable

* feat: allow use caption field as modal title

* refactor: make maskClosable a variable

* fix: use "true"

* fix: code style

* docs: add description about maskClosable

* fix: convention is to have double quotes for strings in the TW core

* refactor: using a "mask-closable" field on the modal tiddlers instead of as a message parameter

* docs: move to modal tid

* Update WidgetMessage_ tm-modal.tid

core/ui/SwitcherModal.tid

@@ -1,6 +1,7 @@
 title: $:/core/ui/SwitcherModal
 subtitle: <$text text={{{[<switch>lookup[$:/language/Switcher/Subtitle/]]}}}/>
 class: tc-modal-centered
+mask-closable: yes
 
 <$tiddler tiddler={{{[<switch>lookup[$:/config/SwitcherTargets/]]}}}>