fix: use fastRelativePath when processing ignore paths

An ignore path can be relative.

For example:

- folder can be `/foo/configs`
- file can be `/foo/src/index.ts`
- the ignore file can be `/foo/configs/.prettierignore`
- the ignore contents can be `../src/index.ts`

This means we end up doing:

```
// does not fall back to path.relative
fastRelativeChildPath('/foo/configs', '/foo/src/index.ts');
```

Which fails since we actually need `fastRelativePath`:

```
// falls back to path.relative
fastRelativePath('/foo/configs', '/foo/src/index.ts');
```

Author: 43081j

src/config_ignore.ts

@@ -27,7 +27,7 @@ const getIgnoresContentMap = async (foldersPaths: string[], filesNames: string[]
 const getIgnoreBy = (folderPath: string, filesContents: string[]): Ignore => {
   const ignore = fastIgnore(filesContents);
   return (filePath: string): boolean => {
-    const fileRelativePath = fastRelativeChildPath(folderPath, filePath);
+    const fileRelativePath = fastRelativePath(folderPath, filePath);
     return !!fileRelativePath && ignore(fileRelativePath);
   };
 };