Add OpenShift-specific section to the README, & spruce up docs

[JohnStarich]

Here's what the preview looks like for operator hub:

[codecov]

Codecov Report

Merging #182 into master will increase coverage by 0.97%.
The diff coverage is 42.43%.

@@            Coverage Diff             @@
##           master     #182      +/-   ##
==========================================
+ Coverage   41.46%   42.43%   +0.97%     
==========================================
  Files          13        5       -8     
  Lines        1423      879     -544     
==========================================
- Hits          590      373     -217     
+ Misses        714      417     -297     
+ Partials      119       89      -30     

Impacted Files	Coverage Δ
controllers/configmap.go	0.00% <0.00%> (ø)
controllers/secret.go	17.85% <17.85%> (ø)
controllers/binding_controller.go	36.47% <36.47%> (ø)
controllers/service_controller.go	48.71% <48.71%> (ø)
controllers/token_controller.go	74.13% <74.13%> (ø)

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[vazirim]

LGTM