Add readonly mode for editor

[ponyr1der]

Description

At this moment editor works only in edit mode, which means that we can't prevent user from making changes, if he is not allowed to make changes.

Proposal

Add readonly property to MarkdownEditorView

[makhnatkin]

@ponyr1der We have a demo mode in the demo folder. But this issue concerns disabling editing mode.

Is the preview from the demo suitable?
Or do you need to disable the mode? For what purpose? Can you provide use cases?

[ponyr1der]

I tried Preview using YfmStaticView, but it's not exactly what i need. I need a mode, where user can't change content of the markup, can only view, scroll, copy, and do other things, that do not mutate markup.

As an example - secure mode in Excel. If u download some xlsx file - it opens in secure (view only) mode, where you can view content, but can't make changes. To be able to change contect - you have to press button "Allow editing", and then Excel changes it's mode and you are able to make changes.

There is a lot of use cases for this feature, exactly mine one is that i need to prevent some users from making changes, but need to let them view content.