add jpeg module

[kuepe-sl]

This PR adds the jpeg dependency, thus enabling the build of the gstjpeg module that allows for JPEG de-/encoding.

Checklist

• Used a personal fork of the feedstock to propose changes
• Bumped the build number (if the version is unchanged)
• Reset the build number to 0 (if the version changed)
• Re-rendered with the latest conda-smithy (Use the phrase @conda-forge-admin, please rerender in a comment in this PR for automated rerendering)
• Ensured the license file is being packaged.

[conda-forge-linter]

Hi! This is the friendly automated conda-forge-linting service.

I just wanted to let you know that I linted all conda-recipes in your PR (recipe) and found it was in an excellent condition.

[kuepe-sl]

@conda-forge-admin, please rerender

[kuepe-sl]

The Windows build should succeed after conda-forge/jpeg-feedstock#31 is merged.

[kuepe-sl]

It looks like the libjpeg Windows patch may need some additional work and/or discussion.
Thus I implemented a fallback mechanism into the GStreamer JPEG import module that is able to find libjpeg without the need for a CMake or pkg-config module.

From my side this ready now.

[andfoy]

@kuepe-sl, thanks for this contribution. It looks good to me