Help wanted: code linting errors (Swift/Typescript)

I've added code linting to make it like other capacitor-community projects.

Unfortunately there are many linting errors, and I need your help to fix them.

### How to help
1. Clone this repository
2. Checkout branch [code-formatting](https://github.com/capacitor-community/camera-preview/tree/code-formatting)
3. Run `npm run lint` to run all linters
4. Fix what it reports 😄
5. Run `npm run lint` again to check they're fixed
6. Submit a new pull request with your changes 🥳