LibWeb: Add missing includes

This remained undetected for a long time as HeaderCheck is disabled by
default. This commit makes the following file compile again:

    // file: compile_me.cpp
    #include <LibWeb/HTML/CrossOrigin/CrossOriginOpenerPolicy.h>
    // That's it, this was enough to cause a compilation error.

Likewise for most other files touched by this commit.

Userland/Libraries/LibWeb/CSS/UnicodeRange.h

@@ -7,6 +7,7 @@
 #pragma once
 
 #include <AK/Assertions.h>
+#include <AK/String.h>
 
 namespace Web::CSS {
 

Userland/Libraries/LibWeb/Forward.h

@@ -454,6 +454,7 @@ class URLSearchParamsIterator;
 }
 
 namespace Web::Bindings {
+class CallbackType;
 class LocationObject;
 class OptionConstructor;
 class RangePrototype;

Userland/Libraries/LibWeb/HTML/CrossOrigin/CrossOriginOpenerPolicy.h

@@ -6,6 +6,8 @@
 
 #pragma once
 
+#include <AK/String.h>
+
 namespace Web::HTML {
 
 // https://html.spec.whatwg.org/multipage/origin.html#cross-origin-opener-policy-value

Userland/Libraries/LibWeb/HTML/CrossOrigin/CrossOriginOpenerPolicyEnforcementResult.h

@@ -7,6 +7,7 @@
 #pragma once
 
 #include <AK/URL.h>
+#include <LibWeb/HTML/CrossOrigin/CrossOriginOpenerPolicy.h>
 #include <LibWeb/HTML/Origin.h>
 
 namespace Web::HTML {

Userland/Libraries/LibWeb/HTML/Parser/HTMLEncodingDetection.h

@@ -8,6 +8,7 @@
 
 #include <AK/Optional.h>
 #include <AK/String.h>
+#include <LibJS/Heap/GCPtr.h>
 #include <LibWeb/Forward.h>
 
 namespace Web::HTML {

Userland/Libraries/LibWeb/HTML/SandboxingFlagSet.h

@@ -6,6 +6,8 @@
 
 #pragma once
 
+#include <AK/Types.h>
+
 namespace Web::HTML {
 
 // https://html.spec.whatwg.org/multipage/origin.html#sandboxing-flag-set

Userland/Libraries/LibWeb/IntersectionObserver/IntersectionObserver.h

@@ -6,6 +6,7 @@
 
 #pragma once
 
+#include <LibJS/Heap/Handle.h>
 #include <LibWeb/Bindings/PlatformObject.h>
 
 namespace Web::IntersectionObserver {

Userland/Libraries/LibWeb/Layout/InlineLevelIterator.h

@@ -9,6 +9,7 @@
 #include <AK/Noncopyable.h>
 #include <LibWeb/Layout/BlockContainer.h>
 #include <LibWeb/Layout/InlineNode.h>
+#include <LibWeb/Layout/LayoutState.h>
 #include <LibWeb/Layout/TextNode.h>
 
 namespace Web::Layout {