Improve trusted-replace-outbound-text scriptlet

When the replacement starts with `json:`, it will be first
decoded using JSON.parse(). Example:

example.com##+js(trusted-replace-outbound-text, somefn, json:"ok")

The doublequotes are required since this is what JSON.parse()
expects as a valid JSON string.

assets/resources/scriptlets.js

@@ -4906,14 +4906,17 @@ builtinScriptlets.push({
 });
 function trustedReplaceOutboundText(
  propChain = '',
- pattern = '',
- replacement = '',
+ rawPattern = '',
+ rawReplacement = '',
  ...args
 ) {
  if ( propChain === '' ) { return; }
  const safe = safeSelf();
- const logPrefix = safe.makeLogPrefix('trusted-replace-outbound-text', propChain, pattern, replacement, ...args);
- const rePattern = safe.patternToRegex(pattern);
+ const logPrefix = safe.makeLogPrefix('trusted-replace-outbound-text', propChain, rawPattern, rawReplacement, ...args);
+ const rePattern = safe.patternToRegex(rawPattern);
+ const replacement = rawReplacement.startsWith('json:')
+ ? safe.JSON_parse(rawReplacement.slice(5))
+ : rawReplacement;
  const extraArgs = safe.getExtraArgs(args);
  const reCondition = safe.patternToRegex(extraArgs.condition || '');
  const reflector = proxyApplyFn(propChain, function(...args) {
@@ -4923,7 +4926,7 @@ function trustedReplaceOutboundText(
  try { textBefore = self.atob(encodedTextBefore); }
  catch(ex) { return encodedTextBefore; }
  }
- if ( pattern === '' ) {
+ if ( rawPattern === '' ) {
  safe.uboLog(logPrefix, 'Decoded outbound text:\n', textBefore);
  return encodedTextBefore;
  }