Add custom booklet headers/footers feature

The headers/footers are defined with the |customHeader| and
|customFooter| keys respectively in the concert JSON definition.

Change-Id: I461266ca8680a1b79abc85e004c92b810a4782fd
2 files changed
tree: f9d18fbb7e043b92a5722df1980412a72246660a
  1. concerts/
  2. css/
  3. img/
  4. js/
  5. tools/
  6. index.html
  7. manifest.json
  8. robots.txt
  9. sw.js