test cases for various environment issues

[pngwn]

Quite a few issues around different environments have been created over time. Some of the are basic things that I should have fixed earlier, some are a little more complex (windows paths etc).

The current rewrite is more agnostic about environment and doesn't assume node like the current library does and will be ESM only, but it would still be good to have some solid test cases for the following issues:

• Error during build with sveltekit2 #565
• getting "require is not defined" when running sveltekit app inside a docker container #540
• ReferenceError: process is not defined #477
• Compile, Mdsvex imports error on Join #412
• Getting Vite error on when importing compile #255