Create Dockerfile

[jmauerhan]

Fixes

Work on Issue #49

Checklist

• I have made a material change to the repo (functionality, testing, spelling, grammar)
• I have read the [Contribution Guide] and my PR follows them.
• I updated my branch with the master branch.
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation about the functionality in the appropriate .md file
• I have added in line documentation to the code I modified

Short description of what this PR does:

• I have added a Dockerfile to allow local development in Docker for this repo. However, I'm not familiar with the repo so I'm not entirely sure this meets your needs, but hopefully it's a starting point.

[jmauerhan]

The documentation requested about how to run it would be:

• build: docker build -t client .
• run : docker run client php examples/example.php

But I'm not sure which .md file you wanted this in

[thinkingserious]

Hello @jmauerhan,

Thanks again for the PR!

We appreciate your contribution and look forward to continued collaboration. Thanks!

Team SendGrid DX