jshint: add 'Blob' and 'FileReader' to pre-defined list
jshint: add 'Blob' and 'FileReader' to pre-defined list

These functions are already defined, and shouldn't be flagged as
"undefined" by the linter.

Signed-off-by: Sean Cross <d7e19930cc1f42c2d0781f4d9e6f1fe5891bf9cf@xobs.io>

chibitronics/ltc-webview-layer,chibitronics/ltc-webview-layer,chibitronics/ltc-webview-layer,chibitronics/ltc-webview-layer