Invalid conversion to uBO syntax - `[$path]`

Matching "the main page only" `[$path]` should be converted to `:matches-path(/^/$/)`
uBO's example: https://github.com/gorhill/ublock/wiki/Procedural-cosmetic-filters#subjectmatches-patharg:~:text=%3Amatches%2Dpath(/%5E/%24/)

Original
```adblock
[$path]fontanka.ru#?#.gridContainer > div[class*="grid"]:has(> section[class^="baseBlock_"] > a[href]:contains(/^(Новости компаний|Фонтанка PRO)$/))
```

Converted to uBO:
```adblock
fontanka.ru#?#:matches-path(/^/$/) .gridContainer > div[class*="grid"]:has(> section[class^="baseBlock_"] > a[href]:contains(/^(Новости компаний|Фонтанка PRO)$/))
```