Eliminate the need for extra escapes in regular expressions

[scripthunter7]

Currently, in the modifiers, we have to escape some special characters from the adblock syntax in the regexps. Two typical things cause misunderstandings:

• the $ sign
• and the comma in the regexp length specifier

In the future, we need to introduce a special tokenization procedure in the parser that works without escaping these characters.

reference: AdguardTeam/VscodeAdblockSyntax#131