TinyMCE readonly mode

[bjarnef]

Prerequisites

• I have added steps to test this contribution in the description below

If there's an existing issue for this PR then this fixes issues described here #17531

Description

TinyMCE property editor supports readonly mode, but it didn't work, because it sets readonly: 1.
According to documentation https://www.tiny.cloud/docs/tinymce/6/editor-important-options/#readonly readonly is a boolean property, so value should be true/false.

Readonly mode of TinyMCE allows to select/highlight text, but not edit, insert/paste, use toolbar actions or shortcuts to modify content.

Before

After

Tested with TheStarterKit package and include the following SendingContentNotification handler and composer in Umbraco.Web.UI project: Test.zip

It may not strictly require to set toolbar: false, but perhaps it was so make it simpler in readonly mode?

// Readonly mode
//baseLineConfigObj.toolbar = vm.readonly ? false : baseLineConfigObj.toolbar;
baseLineConfigObj.readonly = vm.readonly ? true : baseLineConfigObj.readonly;

With this code it looks like this:

[github-actions]

Hi there @bjarnef, thank you for this contribution! 👍

While we wait for one of the Core Collaborators team to have a look at your work, we wanted to let you know about that we have a checklist for some of the things we will consider during review:

• It's clear what problem this is solving, there's a connected issue or a description of what the changes do and how to test them
• The automated tests all pass (see "Checks" tab on this PR)
• The level of security for this contribution is the same or improved
• The level of performance for this contribution is the same or improved
• Avoids creating breaking changes; note that behavioral changes might also be perceived as breaking
• If this is a new feature, Umbraco HQ provided guidance on the implementation beforehand
• 💡 The contribution looks original and the contributor is presumably allowed to share it

Don't worry if you got something wrong. We like to think of a pull request as the start of a conversation, we're happy to provide guidance on improving your contribution.

If you realize that you might want to make some changes then you can do that by adding new commits to the branch you created for this work and pushing new commits. They should then automatically show up as updates to this pull request.

Thanks, from your friendly Umbraco GitHub bot 🤖 🙂