Removed 'regex' and 'lazy_static' dependency

[nptr]

I noticed that insert_dual_endings() pulls in two dependencies (including a full regex engine) for a task that doesn't really justify their use. As a friend of independent applications and libraries I'd welcome if those two crates can be removed.

Of course the new algorithm passes the unit tests. If you are wondering about the len+ 2 in String::with_capacity(), I though i'd leave room for two inserts before causing an allocation.

[NoraCodes]

Clearly a good change; I have a quick style change in https://github.com/nptr/libui-rs/pull/1