http: Add priority to common http headers

The standard `Priority` header is defined in RFC 9218.

This is added as part of the precusor to quic/http3 work.

Signed-off-by: James M Snell <jasnell@gmail.com>

Author: jasnell

src/node_http_common.h

@@ -78,7 +78,8 @@ class Environment;
   V(ORIGIN, "origin")                                                         \
   V(PURPOSE, "purpose")                                                       \
   V(TIMING_ALLOW_ORIGIN, "timing-allow-origin")                               \
-  V(X_FORWARDED_FOR, "x-forwarded-for")
+  V(X_FORWARDED_FOR, "x-forwarded-for")                                       \
+  V(PRIORITY, "priority")
 
 #define HTTP_ADDITIONAL_HEADERS(V)                                            \
   V(ACCEPT_CHARSET, "accept-charset")                                         \

test/parallel/test-http2-binding.js

@@ -180,6 +180,7 @@ const expectedHeaderNames = {
   HTTP2_HEADER_PURPOSE: 'purpose',
   HTTP2_HEADER_TIMING_ALLOW_ORIGIN: 'timing-allow-origin',
   HTTP2_HEADER_X_FORWARDED_FOR: 'x-forwarded-for',
+  HTTP2_PRIORITY: 'priority',
 };
 
 const expectedNGConstants = {