docs: Add Conda badge to README

[eduardo-rodrigues]

The badges updated will now show in orange as for example in Particles README.

* Add conda-forge badge to README
   - c.f. https://github.com/conda-forge/pylhe-feedstock

[codecov]

Codecov Report

Base: 85.71% // Head: 85.71% // No change to project coverage 👍

Coverage data is based on head (f260560) compared to base (a2635c7).
Patch has no changes to coverable lines.

❗ Current head f260560 differs from pull request most recent head 57276f2. Consider uploading reports for the commit 57276f2 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #150   +/-   ##
=======================================
  Coverage   85.71%   85.71%           
=======================================
  Files           2        2           
  Lines         217      217           
  Branches       57       57           
=======================================
  Hits          186      186           
  Misses         27       27           
  Partials        4        4           

Flag	Coverage Δ
unittests-3.10	85.25% <ø> (ø)
unittests-3.6	83.96% <ø> (ø)

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[matthewfeickert]

LGTM. 👍 Thanks!