Add a commit details view

[d13]

Now:

• [x] Open from "show" menu
• [ ] Title: ensure its escaped and linkified
• [x] Add boxed treatment to commit message, highlight first line and honor formatting (whitespace, tabs, etc)
• [x] Theme colors to match VSCode tree views
• [x] Avatar styling
• [x] Hide committer (for now) and change "authored" to "committed"
• [ ] Skeletons for autolinks and associated PR?
• [ ] Distinguish PRs from autolinks
• [x] Empty state message for autolinks
• [x] Create defined sections for autolinks and files with subheadings
• [ ] Dates: honor settings for relative/absolute and formats
• [x] Add sha
• [ ] Follow mode toggle
  • watches selected commit in graph || active line > activeEditor
  • add arg to control whether the view should continue to follow
• [ ] Find all the places we should be able to open the commit details & graph @eamodio
  • opening from the visual file history / timeline view
  • open from status bar
• [ ] Selected state for files to match vscode
• [ ] Keyboard up/down (space for select) in files list

Soon:

• [ ] Keyboard a11y to match VSCode tree views (action groups, focus states)
• [ ] Empty states for autolinks to connect rich provider or configure autolinks
• [ ] Grouping toggle for tree/list/compact
• [ ] Add parent sha (copy or navigate?)

Later:

• [ ] Get presence in avatars
• [ ] add a copy web-component
• [ ] Add copy action for authors, issues and pull requests
• [ ] Clamped titles should be expandable
• [ ] Add overall insertions and deletions along with file stats
• [ ] Multi-select files
• [ ] Collapsable sections for autolinks, files, etc
• [ ] Navigating prev/next commits in time
• [ ] Support co-authors (group co-authors like github authors)
• [ ] Show magnitude of changes like git log --stat