add a “webpack:analyze” command to package.json 
add a “webpack:analyze” command to package.json 

This is so other people can generate that webpack chunk webpage that
shows how big all the chunks are and what is in them

Test plan:
* either run script/nuke_node.sh or compile_assets or in some other way,
  make sure your public/javscripts/translations files are up to date
* then run `yarn webpack:analyze`
* it should work for a few minutes then open a page that shows cool
  webpack chunk stats in your browser

Change-Id: Ia070e373d81aaeec2131e8e299f82515cff57fa4
Reviewed-on: https://gerrit.instructure.com/193087
Tested-by: Jenkins
Reviewed-by: Brent Burgoyne <bccf16d7abdd2611580b1cd7d7a6fcc150d619da@instructure.com>
QA-Review: Brent Burgoyne <bccf16d7abdd2611580b1cd7d7a6fcc150d619da@instructure.com>
Product-Review: Ryan Shaw <ea3cd978650417470535f3a4725b6b5042a6ab59@instructure.com>

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