[docs] Use of mdinclude directive to add .md files to sphinx docs

[rpanderson]

Description

Partially resolves #275.

Proposed Changes

Use the mdinclude directive of m2r, per readthedocs/recommonmark#191 (comment) for including benchmarks/ecg_preprocessing/README.md on the Benchmarks page. To make this work, I had to additionally:

• Use HTML for any hyperlinks in bold/italics;
• Remove blank lines from references div; and
• Relative link figures from docs directory, i.e. prepend ../../benchmarks/ecg_preprocessing to image paths.

The latter does not break images on the modified README when viewed on GitHub as the relative link coincidentally resolves the same file from both locations.

Checklist

• I have read the CONTRIBUTING file.
• My PR is targetted at the dev branch (and not towards the master branch).
• I ran the CODE CHECKS on the files I added or modified and fixed the errors found isort, black, and flake8 failed for reasons unrelated to my modifications. Happy to fix but not including in this PR initially.

[rpanderson]

Sorry, @DominiqueMakowski; I neglected to target dev branch when opening this PR (I did originally but didn't when re-composing the PR after closing my browser tab). Could you please change the base branch? Also, is there any reason you haven't set dev as your default branch?

[DominiqueMakowski]

Could you please change the base branch?

I didn't even know I could do that, thanks a lot haha!

Also, is there any reason you haven't set dev as your default branch?

I don't know (GitHub isn't my strength ^^), would it affect the repo in any other way?

Before I merge, please consider adding yourself to the contributors ☺️

[codecov-commenter]

Codecov Report

Merging #291 into dev will increase coverage by 0.05%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##              dev     #291      +/-   ##
==========================================
+ Coverage   85.45%   85.51%   +0.05%     
==========================================
  Files         156      156              
  Lines        7116     7116              
==========================================
+ Hits         6081     6085       +4     
+ Misses       1035     1031       -4     

Impacted Files	Coverage Δ
neurokit2/rsp/rsp_simulate.py	99.10% <0.00%> (+3.57%)	⬆️

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[rpanderson]

I didn't even know I could do that, thanks a lot haha!

Neither did I until I made the targetted the wrong branch!

Also, is there any reason you haven't set dev as your default branch?

I don't know (GitHub isn't my strength ^^), would it affect the repo in any other way?

I'm not an authority on this, but it doesn't seem to (aside from affecting git ls-remote). Discussion on the convention abounds (one example of many), but it solves the problem of (from the linked issue) "opening PRs against the wrong branch like I did."

[DominiqueMakowski]

Indeed, from the discussion, it seems that it would make sense for us to set dev as the default, especially since the last release we try to adopt a feature-PR -> dev workflow and to merge to dev only once a feature is "stable", so I reckon dev is stable enough so that it could work as a default. I'll definitely consider that

Anyway, thanks again for your help!! Merging now and welcome onboard 😁