Automatically determine the HTTPSE version to use from latest XPI

[bbondy]

We can use this link:
https://www.eff.org/files/https-everywhere-latest.xpi

Then extract the xpi file as a zip.

Then parse the manifest.json file for the version.

Then always use that dynamically.

This will ensure anytime we build our component, it will always have the latest rules.

[cschanaj]

IMHO, it would be even better if you could utilize the update channel EFF is providing, in order to access the latest rules. The signed rulesets are available at https://www.https-rulesets.org/v1/ and the documentations are here. Though it might require additional effort to incorporate this into the existing code.

[cschanaj]

I have submitted a PR on #7 (comment) with #12 to always build HTTPSE with the latest rulesets