Update contribute.html (#270)
Update contribute.html (#270)

- Added docs-style page to Contribute navigation
 - Corrected some capitalization consistency issues
bazelbuild/bazel-website,bazelbuild/bazel-website,davidzchen/bazel-website,bazelbuild/bazel-website,davidzchen/bazel-website,davidzchen/bazel-website,davidzchen/bazel-website