Add changelog for 1.0.8

[WardBrian]

Submission Checklist

• [x] Run unit tests
• [x] Declare copyright holder and open-source license: see below

Summary

Closes #625. I will run a release whenever this gets approved/merged @mitzimorris @ahartikainen

Copyright and Licensing

Please list the copyright holder for the work you are submitting (this will be you or your assignee, such as a university or company): Simons Foundation.

By submitting this pull request, the copyright holder is agreeing to license the submitted work under the following licenses:

• Code: BSD 3-clause (https://opensource.org/licenses/BSD-3-Clause)

[codecov-commenter]

Codecov Report

Merging #626 (d72fe04) into develop (fb3dfe2) will increase coverage by 0.39%. The diff coverage is n/a.

:exclamation: Current head d72fe04 differs from pull request most recent head fa513fb. Consider uploading reports for the commit fa513fb to get more accurate results

@@             Coverage Diff             @@
##           develop     #626      +/-   ##
===========================================
+ Coverage    80.20%   80.59%   +0.39%     
===========================================
  Files           69       46      -23     
  Lines        10326     7051    -3275     
===========================================
- Hits          8282     5683    -2599     
+ Misses        2044     1368     -676     

Impacted Files	Coverage Δ
a/cmdstanpy/cmdstanpy/cmdstanpy/model.py	89.46% <0.00%> (-0.40%)	:arrow_down:
cmdstanpy/cmdstanpy/utils/cmdstan.py
cmdstanpy/cmdstanpy/cmdstan_args.py
cmdstanpy/cmdstanpy/utils/json.py
cmdstanpy/cmdstanpy/utils/__init__.py
cmdstanpy/cmdstanpy/compiler_opts.py
cmdstanpy/cmdstanpy/utils/data_munging.py
cmdstanpy/cmdstanpy/stanfit/runset.py
cmdstanpy/cmdstanpy/stanfit/gq.py
cmdstanpy/cmdstanpy/stanfit/metadata.py
... and 15 more

:mega: We’re building smart automated test selection to slash your CI/CD build times. Learn more

[WardBrian]

@mitzimorris thoughts on a release soon?