vscode clipboard api + support editor/title for webviews

[akosyakov]

This PR tries to address some issues of using humao.rest-client vscode extension.

• fix [vscode] complete clipboard api #5519: clipboard vscode api
• fix [vscode] support editor/title context menus for web views #5515: support editor/title for webviews

How to test

• install humao.rest-client extension
• create test.http and type into some url
• trigger a send request action
• you should be able to toolbar actions
• when you use them the clipboard should be properly populated (at least in Chrome and Electron)

Known issues

• the active webview is not detected properly right now - [vscode] webview active state is bogus if iframe is focused #5521 because of it toolbar actions for webview does not work always
• test it the light theme, webviews have issues with styles and does not work well in dark theme, see [vscode] webview does not have proper styles  #5518

[akosyakov]

@502647092 could you test #5515, although i think first #5521 has to be resolved, otherwise webviews work really bogusly as for now

[502647092]

The toolbar has been displayed properly.

I don't know how to describe this problem. Maybe it's the plug-in problem.

[502647092]

click webview will print error in console

Uncaught TypeError: Cannot read property 'value' of null
    at getFoldingRangeEnd (VM755 main.js:105)
    at HTMLSpanElement.toggleLines (VM755 main.js:17)

[benoitf]

I've tried with https://marketplace.visualstudio.com/items?itemName=SirTobi.code-clip-ring extension and it's working fine
but as soon as I'm using Command+C and Chrome is asking me to authorize the clipboard, then the shortcut command+c is no longer working (while using Edit/copy is)

[502647092]

@akosyakov
when will it be completed
i need it

[akosyakov]

@502647092 I'm stuck with Monaco migration and don't have time to look at it for next 2 weeks for sure. I'm open to collaboration on it. If someone wants to take it over, please do. It can be additional commits in this PR or another PR against this. I don't care. cc @theia-ide/core

[azatsarynnyy]

@akosyakov I depend on Clipboard API support. Would you mind if I extract the related code from your PR to a separate one?

[akosyakov]

@azatsarynnyy do it, although it does not work well enough, see #5527 (review) I hope you can find a way to improve it to support more browsers.

[akosyakov]

closing it, since it is superseded by #6030 and #5994