Fair tutorial guidelines

[john-shepherdson]

Added initial versions of:

• Creating a FAIR Benchmark and Metrics (needs review by Allyson)
• How create a test (service) following the FTR API (needs a lot more detail from Daniel)
• Defining and Running a FAIR Benchmark Assessment Algorithm (needs review by Mark)

The three tutorials are linked by (back)references.

I was unable to preview them in my environment, so cannot be sure they render as expected.

[dgarijo]

Thanks, I will review next week.

[MarekSuchanek]

@john-shepherdson please fix the issues during the build:

/home/runner/work/docs/docs/docs/commons/fair/tutorials/create-benchmark.rst:247: WARNING: undefined label: 'tutorial_create_metric_tests' [ref.ref]
/home/runner/work/docs/docs/docs/commons/fair/tutorials/define-run-scoring-algorithm.rst:31: WARNING: undefined label: 'tutorial_create_metric_tests' [ref.ref]

If CI is not passing, we will not be merging this.