[FEATURE] screen_recorder: add h.264 software encoder

[ChloeTheFairy]

Submission checklist

• I have searched existing issues and confirmed this has not been requested before.
• I have checked existing pull requests for similar changes.

Feature type

Other

Feature summary

A option for h.264 software encoder in the plugin options.

Motivation / use case

Some systems don't support gpu video encoding, so a option for h264 software encoder could make the screen recorder plugin usable there.

Proposed solution

I haven't looked into the code, but probably as simple as the option and passing that. gpu screen recorder has this option.

Alternatives considered

No response

References / related projects

No response

Additional context

No response