Fix documentation wording issues

[andrewkernel]

Closes #6.

Summary

• fix a grammar issue in the contributor guide
• fix two from a web pages wording issues in the evaluation docs and JOSS article source
• fix a typo in the JOSS article source

Verification

• git diff --check
• searched the touched files for the corrected strings: thouroughly, from a web pages, and Help making

[adbar]

Since we're at it we could check if the docs are up-to-date and complete. Do you have other findings of the same kind?

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (93b98a6) to head (c543bb6).

Additional details and impacted files

@@            Coverage Diff            @@
##            master      #192   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            8         8           
  Lines          827       827           
=========================================
  Hits           827       827           

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