* Delete unused file
* Implement CssUtils
* Inject custom CSS styles
* Add info about custom CSS styles to README
* Add note that ElectronClient/app/app.js is generated
* Add support for Setting.TYPE_BUTTON
* Add buttons in Preferences to open custom CSS files
* Swap custom CSS filenames
* Swap custom CSS filenames
* Wrap "Edit" with translation fn
* Incorporate PR feedback from @laurent22
* Add openOrCreateFile to Settings
* Move openOrCreateFile to shim
* Removing header for now - see https://github.com/laurent22/joplin/pull/2099#discussion_r353120915