Filter skills by keeping members with selected skills.

[CJGutz]

Is your feature request related to a problem? Please describe.
A clear and concise description of what the problem is. Ex. I'm always frustrated when [...]

It can be hard finding members which have a specific skill for a course.

Describe the solution you'd like
A clear and concise description of what you want to happen.

Extend the filter on the member page to also filter on those with specific skills. The current solution only filters on those without the ones listed.

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.