fix: add missing standard-GEM file

Description of the issue:

The .standard-GEM.md file appears to be missing from this repository.

Expected feature/value/output:

The file to be filled in accordingly.

Current feature/value/output:

Missing file.

I hereby confirm that I have:

• [x] Done this analysis in the develop branch of the repository
• [x] Checked that a similar issue does not exist already