Updated version and changelog.md towards v0.8.1

[jvdp1]

Here is a PR that updates the files VERSION and CHANGELOG.md towards the release v0.8.1.

@jalvesz should the DOI being updated? Or will it be done automatically on Zenodo?

[jalvesz]

@jalvesz should the DOI being updated? Or will it be done automatically on Zenodo?

Normally the DOI is automatically updated from here on with every new release

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 68.55%. Comparing base (ed0b0c9) to head (488fa28).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1107      +/-   ##
==========================================
+ Coverage   68.53%   68.55%   +0.01%     
==========================================
  Files         396      396              
  Lines       12746    12746              
  Branches     1376     1376              
==========================================
+ Hits         8736     8738       +2     
+ Misses       4010     4008       -2     

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[jvdp1]

Link to the new release: https://github.com/fortran-lang/stdlib/releases/tag/v0.8.1