Switch from Justfile to Taskfile

[shah]

Replace Justfile with Taskfile for OS-neutral portable tasks.

For example, this replaces just maintain:

deno-task update-deno-deps

We need to replace the rest.

[shah]

With the latest commit I've created a much nicer, type-safe, and "hookable" tasks system based on an EventEmitter strategy.

[shah]

Removed almost all Justfile in favor of type-safe Deno. Only core/design-system/lightning/Justfile left, should be easy to rewrite it soon. Instead of putting acquire-slds-icons into a Taskfile.ts, though, just move it into lightning.ts as a method like acquireAssets or similar and the call that method from Taskfile.ts if necessary. acquireAssets could be a common Design System method across all DSs.