Add a new rule to validate network rule patterns

[Alex-302]

Incorrect usage of |, || is not detected, for example - |||

• Invalid rules
  |||example.com^ - should be ||
https://example.com/ads.js|| - should be | at the end

• Redundant characters

• ||example.com/ads**.js|| - one * is enough, **+ - redundant

• ||*/banners/*$domain=example.com - ||* / |* at the beginning of non-domain like of URL part. In this example one * is required to make the rule non-regexp style (usually at the end).

[scripthunter7]

We also need to validate the use of the * and ^ characters. Also the start and end pointers (|)

Reference:

• https://adguard.com/kb/general/ad-filtering/create-own-filters/#basic-rules-special-characters

@ameshkov @maximtop In the longer term, perhaps we should parse the network rule patterns. Thus, using || incorrectly or using a space/invalid chars within the pattern would result a syntax error. Moreover, the pattern could be fragmented, e.g. like this:
||example.com/*.js^ -> ['||', 'example.com/', '*', '.js', '^']

[scripthunter7]

Unnecessary spaces
AdguardTeam/AdguardFilters@cf07657

Originally posted by @piquark6046 in #13 (comment)