Add option for searching with regex

[sheabunge]

Is your feature request related to a problem? Please describe

No response

Describe the solution you'd like

Allow regular expressions to be used when searching for snippets, potentially using a tag like @regex:, e.g.

 @regex: ^[\b]code\bsnippets[\b]$

Describe alternatives you've considered

No response

Additional context

See https://github.com/codesnippetspro/code-snippets/issues/240