Bridge maintainability project

[Half-Shot]

This is a draft plan to get us back to a reasonably maintainable JS bridge stack

Part One - matrix-bot-sdk

The matrix-bot-sdk needs to be modernized to ease development, especially in a world where we have less time to work on it. The order of things to work on, in order:

1. Drop eslint/linting tools and replace with oxlint/oxfmt
2. Use vitest across codebase.
3. Update dependencies / integrate Renovate.
4. Switch to pnpm
5. Ensure GitHub workflows are working correctly and up to date.

Part Two - matrix-appservice-*

We (Element) also maintain matrix-appservice-node and matrix-appservice-bridge. These projects have heavy overlap with this one, and -bridge consumes both this project and -node. Ideally, we would intern these projects into a single repository and use monorepos to separate out the different layers.

The same steps above would apply to these two.

Once this is done, it should be easier to maintain the whole stack without having to bounce between projects and update them.

[AndrewFerr]

Something else that should be done is to update our modules to use ESM. The main reason for that is how some dependencies (lowdb, ip-cidr) have moved to ESM, and importing them from CommonJS is either impossible or very difficult. The other reason is just because ESM is the Latest Thing™️ and should thus be preferred.