Fix readthedocs builds

[jankrepl]

Since trying to install numpy from a wheel leads to a broken installation, this PR suggests using a system numpy. RTD is installing numpy and other scientific packages inside of their docker image to serve exactly this purpose - there is no need to compile complicated packages from scratch or hope the wheels are valid for the platform.

Probably will break again in the future, but good for now.

See also

• https://hub.docker.com/r/readthedocs/build/dockerfile
• https://docs.readthedocs.io/en/stable/config-file/v2.html?highlight=numpy#python-system-packages

[codecov[bot]]

Codecov Report

Merging #107 (ba0ff87) into master (478776c) will not change coverage. The diff coverage is n/a.

@@            Coverage Diff            @@
##            master      #107   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           18        18           
  Lines         1762      1762           
=========================================
  Hits          1762      1762           

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update 478776c...c078fc8. Read the comment docs.