Add Dojo license to the top of all builds.

[mwistrand]

Type: bug

The following has been addressed in the PR:

• [x] There is a related issue
• [x] All code matches the style guide
• [ ] Unit or Functional tests are included in the PR

Description:

Add src/banner.md that contains any text (e.g., the Dojo license) that needs to be prepended as a comment to the output build source.

Resolves #108

[codecov[bot]]

Codecov Report

Merging #119 into master will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #119   +/-   ##
=======================================
  Coverage   95.59%   95.59%           
=======================================
  Files          11       11           
  Lines         613      613           
  Branches      127      127           
=======================================
  Hits          586      586           
  Misses         14       14           
  Partials       13       13

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[mwistrand]

Verified against todo-mvc-kitchensink and todo-mvc.