feat(esm): support custom conditions

[colinlienard]

Add support for customConditions in ESM.

For example, if a tsconfig contains this:

{
	"compilerOptions": {
		"customConditions": ["source"],
	}
}

passing the condition as an arg to the CLI would not be needed anymore:

- tsx --conditions source src
+ tsx src

But this is only for ESM as explained here: #574 (comment)

Related to #574

[privatenumber]

Thanks for the PR

This is blocked until we add condition support to the CJS resolver though. Since tsx aims to consolidate ESM and CJS, we want to avoid introducing discrepancies between them.

[colinlienard]

I tried adding support for CJS, but it seems quite challenging. Do you have any ideas on how to make it work? @privatenumber