URLs generated for rules in subdirectories in windows uses wrong separator
## Expected result
```
https://html-validate.org/rules/wcag/h32.html
https://html-validate.org/rules/wcag/h30.html
```
## Actual result
```
https://html-validate.org/rules/wcag\h32.html
https://html-validate.org/rules/wcag\h30.html
```
issue