Tiptap RTE: Stylesheets

[leekelleher]

Description

Adds Stylesheet configuration to the Tiptap RTE.

The Stylesheet picker property-editor that is used for the TinyMCE configuration was scoped to the tinymce package, so I've moved (duplicated) the code to add the property-editor to the templating/stylesheets package. I've updated the propertyEditorUiAlias for TinyMCE, so the upcoming community package can reference Umbraco's stylesheet picker.

There are some additional tweaks in this PR whilst I was in the Stylesheet section.

How to test?

Best to test against the server, as the mock-server doesn't have the capability to serve the Stylesheet contents as a static-file (yet). Add a stylesheet (new or existing) to the Tiptap RTE configuration, view the RTE on a document... check that the styles have loaded.

Here's an example CSS that would be visually obvious if it's loaded or not.

#editor, #tinymce {
    background-color: pink;
    font-family: cursive;
}