js2-mode is no longer developed and we recommend js-mode these days,
so switch the modelines to specify that, and make them consistent
across all files.
https://bugzilla.gnome.org/show_bug.cgi?id=660358
libsoup won't check for a valid cert by default, so copy some logic from
glib-networking to check against the system cert list. Additionally, allow a
fallback for developers, ~/.local/share/extensions.gnome.org.crt, for easy
local development of the website.
https://bugzilla.gnome.org/show_bug.cgi?id=658870
Add an entry in config.js.in for PACKAGE_VERSION and GJS_VERSION,
to be used by the notification daemon and in the future by the
extension system.
https://bugzilla.gnome.org/show_bug.cgi?id=639255
