add button to toggle blocked pull requests
add button to toggle blocked pull requests

This commit adds in a button to the navbar similar to the one for
displaying Cyrogenic Storage. It will have an onClick event attribute
which will toggle the filter/view state for externally blocked pull requests
(defaulted to not be shown initially).

iFixit/pulldasher,iFixit/pulldasher,iFixit/pulldasher,iFixit/pulldasher