No regex url check for EmbedBuilder

[xDec0de]

Pull Request Etiquette

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Changes

• [ ] Internal code
• [x] Library interface (affecting end-user code)
• [ ] Documentation
• [ ] Other: _____

Closes Issue: NaN

Description

Just a simple change to avoid using a regex Pattern when checking if a URL is valid on the EmbedBuilder class. Instead, it relies on String#regionMatches (Case insensitive) and a simple length check to have the exact same behaviour as the current pattern. I know this may be considered micro optimization, but I found it and thought it could be an easy first PR for me.