Add links for doc and cheat sheet

[PipKat]

Per Landon’s request in the PyAnsys Global AFT on 7/26/23, add a link to the PyMAPDL cheat sheet from this library's documentation.

Note: This library doesn't reuse the README content in the overall index.rst file for documentation. Consequently, I had to add a new "Documentation and issues" section in both the README and the overall index.rst file.

@germa89 The doc build is failing because it isn't finding the external links specified in examples. I have no idea why the "Remote" checks for build and unit testing are failing.

[codecov]

Codecov Report

Merging #2235 (d7e5873) into main (e3885fb) will increase coverage by 1.32%.
Report is 79 commits behind head on main.
The diff coverage is 93.67%.

@@            Coverage Diff             @@
##             main    #2235      +/-   ##
==========================================
+ Coverage   86.39%   87.72%   +1.32%     
==========================================
  Files          45       45              
  Lines        7977     8300     +323     
==========================================
+ Hits         6892     7281     +389     
+ Misses       1085     1019      -66     

[germa89]

@germa89 The doc build is failing because it isn't finding the external links specified in examples. I have no idea why the "Remote" checks for build and unit testing are failing.

Don't worry @PipKat, I will take care of it 😄

[germa89]

@PipKat feel free to merge whenever you want 😄