add config/WEBPACK to .gitignore
add config/WEBPACK to .gitignore

Change-Id: Ic6fac9f27fc8a531a41ba1dd3b54873135f4aa5b
Reviewed-on: https://gerrit.instructure.com/80496
Reviewed-by: Ethan Vizitei <73eeb0b2f65d05a906adf3b21ee1f9f5a2aa3c1c@instructure.com>
Tested-by: Jenkins
Product-Review: Cody Cutrer <c4fe2b1d90ef8f2548c8aeabfa633434316f0305@instructure.com>
QA-Review: Cody Cutrer <c4fe2b1d90ef8f2548c8aeabfa633434316f0305@instructure.com>

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