Add an attribute in category filter links

[sanjibpanda]

@nwisehart - As we discussed last week, in the new branch you are planning to create for instant app gallery, could you please add an attribute called data-langlabel in category filter link. Category name should be the value for this attribute. It will be great if spaces can be replaced with "-" in value so that we can use it as a slog and localize from client side.