Mac support

[sgmunn]

basic support for scrolling, selection and copy+paste. there are several issues that should be resolved before this is merged, most significantly what to do with tabs and newlines when copying as these are not present in the buffer currently. there are a set of smaller "polish" items that I think should be done as well.

• [x] ~tab and~ newlines should be able to be copied from the buffer
• [x] buffer resize and reflow (related to tab/newlines issue). when the buffer changes we need to reflow the content and reposition soft breaks ~and tabs~
• [x] ~voice over support for the terminal view~
• [x] properly disable scrolling when alt buffer is enabled
• [x] restore scroll position when switching back from alt buffer
• [x] scroll thumb proportion is not correct
• [x] mouse wheel support for scrolling
• [x] scroll paging
• [x] select and scroll at the same time
• [x] cursor is not scrolled properly
• [x] delete stale log files rather than leaving them on disk
• [x] watch the shell process and disable/close the terminal window when the shell exits
• [x] selection should clear when the user types, switches to the alt buffer
• [x] selection logic could moved to a selection service
• [ ] profit

Voice over will be a different PR.

[sgmunn]

I fixed a minor rendering glitch with emoji's, so that they are presented now but the width calculation is off. I am not going to worry about that too much because xterm itself still has issues rendering and calculating widths correctly (see below)

[sgmunn]

https://share.getcloudapp.com/geu2x7NZ

this is ready enough now.