Discard adblock agent properly

[ameshkov]

Currently, we only discard [Adblock, we should discard more:
[AdBlock], [Adblock Plus], [uBlock] / [uBlock Origin], [AdGuard]

See there for the details:
https://github.com/github/linguist/blob/bf853f1c663903e3ee35935189760191f1c45e1c/lib/linguist/heuristics.yml#L681-L700

[ngorskikh]

@ameshkov Hmm, I need more context as to what exactly do we need to solve. If I understand correctly, we are talking about handling the first line of a filter list in the filter list processor? Currently, we just pass that to the engine. It won't parse anyway :)

[ameshkov]

@ngorskikh search for [Adblock in the code.