Add +https directive to urlskip= option

When present, the `+https` directive will force the protocol of the
resulting URL to be `https:`.

Related feedback:
uBlockOrigin/uBlock-issues#3206 (comment)

src/js/static-net-filtering.js

@@ -5424,13 +5424,25 @@ function urlSkip(urlin, steps) {
  try {
  let urlout;
  for ( const step of steps ) {
- if ( step.startsWith('?') === false ) { return; }
- urlout = (new URL(urlin)).searchParams.get(step.slice(1));
- if ( urlout === null ) { return; }
- if ( urlout.includes(' ') ) {
- urlout = urlout.replace(/ /g, '%20');
+ // Extract from URL parameter
+ if ( step.startsWith('?') ) {
+ urlout = (new URL(urlin)).searchParams.get(step.slice(1));
+ if ( urlout === null ) { return; }
+ if ( urlout.includes(' ') ) {
+ urlout = urlout.replace(/ /g, '%20');
+ }
+ urlin = urlout;
+ continue;
  }
- urlin = urlout;
+ // Enforce https
+ if ( step === '+https' ) {
+ const s = urlin.replace(/^https?:\/\//, '');
+ if ( /^[\w-]:\/\//.test(s) ) { return; }
+ urlin = urlout = `https://${s}`;
+ continue;
+ }
+ // Unknown directive
+ return;
  }
  void new URL(urlout);
  return urlout;