aegir should support `.aegir.ts` config file

**Is your feature request related to a problem? Please describe.**
Creating an `.aegir.cjs` or `.aegir.js` config file in a typescript repo is unintuitive and archaic. We should be able to save our aegir config as typescript in a file such as `.aegir.ts`

Without a typescript config file, a typescript repo requires workarounds such as importing only transpiled source, using ts-node/register, or other obtrusive methods.

**Describe the solution you'd like**
Aegir should support creating a config file in typescript `.aegir.ts`. Most modern tools and libraries support typescript config files today.

**Describe alternatives you've considered**
adding
```js
require('ts-node').register({
project: 'tsconfig.json',
})
```
to the top of the `.aegir.cjs` file will allow you to import typescript files, but this shouldn't be required.

**Additional context**
We should fully adopt and encourage typescript usage.