--no-check docs

[lucacasonato]

Closes #6713

[bartlomieju]

We should also mention that developers should use import type and export type for type-only imports/export; otherwise using --no-check will lead to errors as described by @kitsonk in #6456

Please mention config we use in std/ that ensures modules can be safely transpiled:

{
  "compilerOptions": {
    "importsNotUsedAsValues": "error"
  }
}

[kitsonk]

The other thing that is "banned" in transpile only is const enum (as well as the legacy export = and import = TypeScript syntax which is really obscure, and I doubt anyone is trying to use that in Deno, but for completeness 🤷 )

[kitsonk]

LGTM

[ry]

LGTM - nice!