These imports should never result in a real import in the emitted code

Cleans up API and removes some unused features (e.g. paging)
Adds date formatting
Adds loading progress and message
Removes lots of console.logs 😁
Adds titles to diffs

Squashed commit of the following:

commit 76689c23011bf960f5ba3e199659e8180455466d
Author: Pine Wu <octref@gmail.com>
Date:   Fri Jan 24 10:19:44 2020 +0100

    Clarify API

commit 88d772d62da5d912b54285aa52dc6d6a108ca587
Author: Pine Wu <octref@gmail.com>
Date:   Fri Jan 24 10:17:28 2020 +0100

    Tooltip

commit 11ef8012ae3e560d6db6fff26ba3c258e7eae4a6
Author: Pine Wu <octref@gmail.com>
Date:   Thu Jan 23 16:50:28 2020 +0100

    Hover to show link color and use cmd/alt click

commit 38655a70b3eed56b99e8018fb5c79bd41b6c4f56
Author: Pine Wu <octref@gmail.com>
Date:   Thu Jan 23 15:21:13 2020 +0100

    Add hack to always render underline a bit below

commit 959f6b13bf81885cc370f6099e5123142089599e
Author: Pine Wu <octref@gmail.com>
Date:   Thu Jan 23 11:32:37 2020 +0100

    Fix compile error

commit b5c50e872935e74503451bd2801227f82b8410f4
Author: Pine Wu <octref@gmail.com>
Date:   Thu Jan 23 11:19:52 2020 +0100

    Bring code link everywhere for Diagnostics

commit f88cd4cc4e2064fd96853373e26c12670161bf60
Author: Pine Wu <octref@gmail.com>
Date:   Wed Jan 22 17:24:54 2020 +0100

    Add Diagnostic#code2 and render it in hover/inline/panel

commit 2a13e3e4f62fd3707f2c03c1e814a8fdc557c367
Author: Pine Wu <octref@gmail.com>
Date:   Wed Jan 22 13:49:42 2020 +0100

    WIP

Adds a backup method to the custom editor API proposal. This method allows custom editors to hook in to VS Code's hot exit behavior

If `backup` is not implemented, VS Code will assume that the custom editor cannot be hot exited.

When `backup` is implemented, VS Code will invoke the method after every edit (this is debounced). At this point, this extension should back up the current resource.  The result is a promise indicating if the backup was successful or not

VS Code will only hot exit if all backups were successful.

Squashed commit of the following:

commit 2bbee1ef
Author: Pine Wu <octref@gmail.com>
Date:   Wed Jan 22 11:48:44 2020 +0100

    Separate testing changes

commit 047e81e9
Author: Pine Wu <octref@gmail.com>
Date:   Wed Jan 22 11:44:30 2020 +0100

    Tweak layout

commit 078b21f6
Author: Pine Wu <octref@gmail.com>
Date:   Tue Jan 21 15:20:07 2020 +0100

    UI changes

commit a869c0fa
Author: Pine Wu <octref@gmail.com>
Date:   Tue Jan 21 12:28:35 2020 +0100

    WIP

For #88719

With this change, instead of passing custom editor edit json back and forth with the extension host, we keep the original edit objects on the extension host. This means that we can pass extensions back the exact same edit object they first hand to us. It also means that edits no longer need to be json serializable.

- extract a separate DocumentRangeSemanticTokensProvider that deals with a document range
- extract a separate provideDocumentSemanticTokensEdits that deals with updating via SemanticTokensEdits a previous result