[BUG] Numeric references fail in `config.yaml`

[DeepanshKhurana]

Bug Report

Describe the bug
Numeric references to files in any place in the config.yaml e.g. 404 instead of 404.md fail with a function not found error.

To Reproduce
Steps to reproduce the behavior:

1. Add a number to any of the fields e.g. notFound or exclude
2. The build will fail on deployment

Expected behavior
The filenames should parse correctly to markdown references.

Screenshots
N/A

Additional context
N/A