update regex to catch all theme names

[Morgy93]

• Pull request is based against main branch
• README.md reflects changes (if applicable)
• New files contain a license header

Issue

The given regex: /\%theme\((?)([a-zA-Z0-9\/\_]{1,})\)\%/ does not catch - in the theme name.
For example: %theme(frontend/Vendor/my-theme)%

Proposed changes

The new regex: /\%theme\(([^)]+)\)\%/ caches everything between ( and ):

by regex101.com

[therouv]

@Morgy93 Thanks!