[0.6.x] Support loading certificates from environment variables

[innocenzi]

This PR adds support for loading certificates thanks to paths defined in the environment.

Currently, in our team, we use valetTls, which is very nice for us Valet users. But a member of our team uses Windows and Laragon, and cannot benefit from the configuration.

With this PR, they will be able to define VITE_DEV_SERVER_KEY and VITE_DEV_SERVER_CERT in their .env with the paths to their Laragon certificates. That way, there is no need to touch vite.config.ts, so it can keep being environment-agnostic.

Keeping this as a draft to test it on my own Windows machine later - also, not so sure about the variable names: VITE_* environment variables are available in the front-end through import.meta.env.

[innocenzi]

This pull request is ready for review. If you have a better name for VITE_DEV_SERVER_KEY/CERT, feel free to suggest.

[timacdonald]

Seems good to me! I've added some error messages to hopefully guide the user when we cannot find the specified paths or determine the host (instead of silently failing):

[timacdonald]

Thanks for contributing to the core plugin @innocenzi ❤️ you rock.

[timacdonald]

@innocenzi I'm wondering if we should first use the ASSET_URL and then fallback to the APP_URL here?

What do you think?

The official plugin uses the asset helper for all generated URLs.

[innocenzi]

Admittedly I never used ASSET_URL in development myself so I'm not too sure. I imagine it could make sense when using Docker but I don't know the setup :/

I would say, we should probably wait for people with such setups to provide feedback if what the plugin offers doesn't work for them