[api-documenter] Case sensitivity not taken into account

[masad-frost]

export interface X {
  something: string;
}

export function x() {
}

Generating with api-extractor seems to work fine, but when it goes to api-documenter it produces a single x.md file instead of x.md and X.md

[iclanton]

Some filesystems don't support two files or folders that only differ in casing (for example, NTFS on Windows). This is an edge case that should probably be fixed, but isn't a high priority. We'd need to decide the collision resolution strategy. Perhaps one of them could be alt/X.md?

@masad-frost - Thoughts on what the expected output would look like? Would you be willing to contribute a fix?