LibWeb: Add definitions from '2.2.4. Bodies' in the Fetch spec

...at least the ones that don't require an implementation of the Streams
spec :^)

Userland/Libraries/LibWeb/CMakeLists.txt

@@ -119,6 +119,7 @@ set(SOURCES
     Encoding/TextEncoder.cpp
     Fetch/Infrastructure/HTTP.cpp
     Fetch/Infrastructure/URL.cpp
+    Fetch/Infrastructure/HTTP/Bodies.cpp
     Fetch/Infrastructure/HTTP/Headers.cpp
     Fetch/Infrastructure/HTTP/Methods.cpp
     Fetch/Infrastructure/HTTP/Statuses.cpp