refs TryGhost/Team#2904
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### <samp>🤖 Generated by Copilot at 2ba5e2a</samp>
This pull request adds the lexical editor feature to the Ghost admin
app, which allows users to create and edit snippets in a natural
language format. It modifies the `snippet` model, adapter, and
controller, and the `lexical-editor` template and component to support
the new feature.
no issue
- all of our models which allow users to name something use `name` as the field descriptor rather than `title` so `snippet.title` was renamed for consistency
- also fixes typo in the plus-menu component that stopped clicking on snippets from working
closes https://github.com/TryGhost/Team/issues/411
- adds "Create snippet" icon to the editor toolbar
- uses the same link input component design for specifying snippet titles
- snippets are loaded in the background when the editor is accessed
- snippets are listed at the bottom of the card menus of the + and / menus
- clicking a snippet inserts the snippet's contents in place of the current blank section
