Add support for the Trusted Types CSP directives

[ousamabenyounes]

Adds support for the Trusted Types CSP
directives require-trusted-types-for and trusted-types (Fix #233).

Trusted Types help mitigate DOM-based XSS by locking down dangerous DOM sinks.
This lets applications configure the two directives through the bundle's usual
CSP configuration.

What

• Register require-trusted-types-for and trusted-types in
  DirectiveSet::$directiveNames under a dedicated TYPE_TRUSTED_TYPES_LIST
  type. Like other non-source-list directives they are always emitted and never
  deduplicated against default-src.
• Advertise them in PolicyManager::getChromeDirectives() only. Trusted Types
  is currently shipped by Chromium-based browsers, so (with browser_adaptive
  enabled) they are emitted for Chrome/Opera and omitted for Firefox/Safari,
  consistent with how the bundle already gates browser-specific directives.
• Quote the script and allow-duplicates keywords in
  ContentSecurityPolicyParser so require-trusted-types-for: ['script']
  renders as require-trusted-types-for 'script' and the 'allow-duplicates'
  trusted-types keyword is quoted, while custom policy names are left untouched.
• Config wiring and DI are automatic (the config tree is built from
  DirectiveSet::getNames()).
• Document the new directives in Resources/doc/index.rst.

Purely additive, opt-in, no new dependency and no BC break. This revives the
approach from the (now stale) PR #235.

Test verification (RED → GREEN)

New cases in ContentSecurityPolicyParserTest and
DirectiveSetTest::testTrustedTypesDirectives.

RED (unmodified branch, only the tests applied):

2) ...testQuotesKeywords
-''allow-duplicates''
+'allow-duplicates'
3) ...testTrustedTypesDirectives with data set "chrome emits trusted types directives"
-'default-src 'self'; require-trusted-types-for 'script'; trusted-types my-policy 'allow-duplicates''
+'default-src 'self''
Tests: 18, Assertions: 18, Failures: 3

GREEN (with the fix):

..................                                                18 / 18 (100%)
OK (Tests: 18, Assertions: 18)

Full suite: 433 tests green (was 428 + 5 new). PHP-CS-Fixer and
composer-normalize clean; PHPStan reports no new errors.