Do mild editing for grammar, consistency, and Markdown

[mhucka]

In one document, the constructs in a list of cards were not parallel. In other places, just fiddled with constructs that struck me as awkward.

In several *.md files, added missing Markdown code block language tags.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.64%. Comparing base (b199b21) to head (398cdb3).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #7246   +/-   ##
=======================================
  Coverage   98.64%   98.64%           
=======================================
  Files        1106     1106           
  Lines       95990    95990           
=======================================
+ Hits        94687    94690    +3     
+ Misses       1303     1300    -3     

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[pavoljuhas]

LGTM with the correction below to address yamllint. Thank you!

diff --git a/docs/experiments/_index.yaml b/docs/experiments/_index.yaml
index a66e9d42..ff9b9b75 100644
--- a/docs/experiments/_index.yaml
+++ b/docs/experiments/_index.yaml
@@ -29,5 +29,5 @@ landing_page:
     - heading: Variational Quantum Eigensolver
       description: An example of computing the ground state of a Hamiltonian using the
-      variational principle.
+        variational principle.
       path: /cirq/experiments/variational_algorithm
     - heading: Quantum Walks