Tweak styling of Skylark rule READMEs to be consistent when viewed on external site.
Tweak styling of Skylark rule READMEs to be consistent when viewed on
external site.

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MOS_MIGRATED_REVID=106135529

sdtwigg/rules_scala,sdtwigg/rules_scala,ianoc/rules_scala,smparkes/rules_scala,sdtwigg/rules_scala,bazelbuild/rules_scala,bazelbuild/rules_scala,ianoc/rules_scala,smparkes/rules_scala,ianoc/rules_scala,bazelbuild/rules_scala,smparkes/rules_scala