Add support for highlighting `angular-ts` and `angular-html` blocks in markdown files

Prettier added in their [v3.8.0](https://prettier.io/blog/2026/01/14/3.8.0) support for formatting `angular-ts` and `angular-html` fenced code blocks.

Now we're only missing proper highlighting which the vscode extension should be able to provide.

Start by locating the VS Code extension's markdown syntax-highlighting definitions and review how fenced language identifiers are mapped. Add support for `angular-ts` and `angular-html`, then verify that both fenced blocks receive proper highlighting in markdown files.

Written by the indexing model from the issue text.