fix: sync the absolutePath file URL prefix with schema-utils (#50)

The hoisted copy wanted exactly two slashes and a lower-case scheme, so a
pre-compiled schema rejected `file:/abs` and `FILE:///abs` where the real
keyword now takes both. The lookahead leaves the first slash to the path
part, keeping a scheme with nothing absolute after it rejected.

Author: alexander-akait

precompile-schemas/index.js

@@ -131,7 +131,7 @@ const postprocess = async (code) => {
 	// Keep in sync with the `absolutePath` keyword of `schema-utils`, the
 	// pre-compiled schema has to accept exactly what the real one accepts
 	if (/absolutePathRegExp/.test(code))
-		code = `const absolutePathRegExp = /^(?:file:\\/\\/)?(?:[A-Za-z]:[\\\\/]|\\\\\\\\|\\/)/;${code}`;
+		code = `const absolutePathRegExp = /^(?:file:(?=\\/))?(?:[A-Za-z]:[\\\\/]|\\\\\\\\|\\/)/i;${code}`;
 
 	// remove unnecessary error code:
 	code = code