Follow JS implementation.

[Foxboron]

Current the JS implementation uses several values:
prefix, suffix, source, modifiers
where the add method compiles the regex pattern into its correct form.

consider end_of_line().find("a")
Currently the python implementation will generate $a while the JS version will generate "a$".
Considering the current implementation, it would require minimal effort to mimic this behavior better.

[metal3d]

There is other methods that are not implemented in several implementation, as "begin/endCapture".

I asked for an implementation doc repository that has been created. Maybe we should discuss