added additional info for custom http headers

[cemenson]

Hi all,

First pull request (ever). Love grpc-gateway, keep up the great work!

I've made a couple of tiny changes to the "Customizing Your Gateway" docs page:

1. Added a HeaderMatcherFunc example, showing a couple of ways of returning the custom header key.
2. Added a small example of sending a response header from the server using gRPC.SendHeader() as well as a small pointer to the gRPC metadata docs for more info.

That's it! It would have help me a little if they were there when I was setting this up for the first time, so I'm hoping this will help others.

Thanks!

[codecov-io]

Codecov Report

Merging #1035 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1035   +/-   ##
=======================================
  Coverage   53.62%   53.62%           
=======================================
  Files          40       40           
  Lines        4052     4052           
=======================================
  Hits         2173     2173           
  Misses       1674     1674           
  Partials      205      205

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[achew22]

@cemenson welcome to the party! 🎉 🎈 🎉

This is a great first PR on a project and great first contribution to the open source world. Thank you so much for taking the time to fix something that didn't look right. This is how open source gets better.

I look forward to your next PR, and if there is anything I can do to have it be one that enhances this project, just let me know.

Thanks again!

[cemenson]

Thanks @achew22! Glad to help!

[cemenson]

Sorry, such a noob. Am I supposed to close this PR?

[achew22]

No, but I appreciate your trying to help. On my side there is a "merge" button which I needed to hit. However, I wanted to make sure the tests passed before submitting. Sorry I forgot about this tab and just got back to it. It should be merged now in the master branch of the repo.