Re-do webviews (config pane and find-panel) and their key capture behaviors

[boltex]

Use the new toolkit for webview to redo the find panel and settings panel:

Webview UI Toolkit for Visual Studio Code#

The Webview UI Toolkit for Visual Studio Code is a component library for building webview-based extensions in Visual Studio Code.

Also change key capture behaviors with this new api:

Use this new api feature for webview (find panel) command conditions - > remove current key captures from inside the webview.

New activeWebviewPanelId context key #

The new activeWebviewPanelId context key tracks the viewType of the currently focused webview panel. You can use it in when clauses to enable commands or menu items when your webview is focused.

"when": "activeWebviewPanelId == 'markdown.preview'"