Development: Create infrastructure for client plugins

[Anatoly03]

This Pull Request will evolve the first building blocks of client plugins infrastructure. The following ideas will be implemented.

• General Plugin API. A Torii-native system for loading, dispatching, running and offloading extensions. Plugins should have access to the following underlying infrastructure.
  • TipTap.
  • ProseMirror.
  • Settings.
  • Localisation Extensions.
  • Themes & CSS.
• View Anchors. An idea where the main application has several "anchor views", all with a unique ID, and the plugins can append elements that the anchor views will render. Sidebar buttons, footers, main views are all anchor points.

This Pull Request has a huge scope, so the overall ADHD-friendly approach will be to divide the Pull Request into smaller scopes, overall consisting of the following phases.

Phase 1: Plugin API Core

• ToriiPlugin: A separate library module defining plugin.
• Define plugin lifecycle hooks (onInit, onRecordOpen, onComponentUpdate, etc.)
• Define anchor point constants. Anchor points are views which can be extended by plugins.
• PluginManager with register new plugins and getAnchorView() to render an anchor

Phase 2: Call Plugin API

• Define a Vue anchor component (renderer) and place some in the app.
• Pass workspace context to plugins.

Phase 3: Plugin Extraction

• word-count
• recent-projects