Web: Mobile Safari support

This is a meta issue for our Safari (on iOS/iPadOS) support ([issue list](https://github.com/microsoft/vscode/issues?utf8=✓&q=is%3Aopen+is%3Aissue+label%3Asafari+label%3Aios+)) and this can be used to track the limitations and gaps we see today on mobile / touch screens. **_updated Oct 2020._** To enable users to use the Web UI in Safari on iOS for some basic work, we need to fix the following blocking issues **Blockers** * [ ] :hand: Missing `wheel` event https://github.com/microsoft/vscode/issues/106232 (upstream https://bugs.webkit.org/show_bug.cgi?id=210071 ) * [ ] Blockers on Safari desktop https://github.com/microsoft/vscode/issues/108637 * [ ] :runner: Workbench size inconsistent with visual viewport https://github.com/microsoft/vscode/issues/108267 * [ ] :runner: Port forwarding blocked https://github.com/MicrosoftDocs/vscodespaces/issues/728 * No authentication flow as it can't open a new window * can not debug extensions * [ ] UI affordance fallback for `cursor: ` styles https://github.com/microsoft/vscode/issues/108832 * [ ] Drag & Drop views/panels with mouse events https://dvcs.w3.org/hg/d4e/raw-file/tip/mouse-event-test.html **Bugs** * [ ] Touch/pointers not working (Settings Editor dropdown, view header, etc) https://github.com/microsoft/vscode/issues?q=is%3Aopen+label%3Atouch%2Fpointer+label%3Aios * [ ] MISC https://github.com/microsoft/vscode/issues?q=is%3Aopen+label%3Aios+label%3Abug+-label%3Atouch%2Fpointer --- With above items finished, users can use the Web UI for basic tasks if they us an external keyboard and mouse. However if you are not using an external keyboard with Escape and Function keys, or a mouse/pointer device, you can easily find the Web UI **difficult** to use and you can't be as productive as on the desktop. Major **blockers** are: * Escape. Escape key is the major key for hiding UI elements in the workbench. For native elements, iOS may know how to map `Ctrl+[` to behave the same as Escape, however for our keybinding service…