.jshintrc

configitems: register server.zstdlevel

Somehow, I managed to trigger a devel-warn running `hg serve` outside the test
suite on one of the repos generated by running test-lfs-serve-access.t --keep.
(I'm not hitting it now after doing a `make local`.)  The only reference to this
in all of the history is the help text added in e75463e3179f, and the
translations.  (It looks like the string is built dynamically with '%slevel',
which is probably how this was missed.  I wonder if this isn't getting routed to
error.log for some reason.)

In any event, server.zliblevel is registered, and that's required to pick up the
documented default.

{
    // Enforcing
    "eqeqeq"        : true,     // true: Require triple equals (===) for comparison
    "forin"         : true,     // true: Require filtering for..in loops with obj.hasOwnProperty()
    "freeze"        : true,     // true: prohibits overwriting prototypes of native objects such as Array, Date etc.
    "nonbsp"        : true,     // true: Prohibit "non-breaking whitespace" characters.
    "undef"         : true,     // true: Require all non-global variables to be declared (prevents global leaks)

    // Environments
    "browser"       : true      // Web Browser (window, document, etc)
}