doc: add http highlight grammar

Prior to this commit, http request message code blocks in Markdown
files were not being highlighted correctly. This has been corrected by
adding the new grammar to the bundle, removing the CRLFs (`\r\n`) from
these code samples, adding a reminder to re-add them, and tuning the
syntax theme to support attribute highlighting.

PR-URL: #33785
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

doc/api/http.md

@@ -2090,13 +2090,13 @@ added: v0.1.90
 
 **Only valid for request obtained from [`http.Server`][].**
 
-Request URL string. This contains only the URL that is
-present in the actual HTTP request. If the request is:
+Request URL string. This contains only the URL that is present in the actual
+HTTP request. If the request is (remember, each header line ends with `\r\n`
+plus a final `\r\n` after the last one indicating the end of the header):
 
 ```http
-GET /status?name=ryan HTTP/1.1\r\n
-Accept: text/plain\r\n
-\r\n
+GET /status?name=ryan HTTP/1.1
+Accept: text/plain
 ```
 
 To parse the URL into its parts:

doc/api/http2.md

@@ -3027,13 +3027,13 @@ added: v8.4.0
 
 * {string}
 
-Request URL string. This contains only the URL that is
-present in the actual HTTP request. If the request is:
+Request URL string. This contains only the URL that is present in the actual
+HTTP request. If the request is (remember, each header line ends with `\r\n`
+plus a final `\r\n` after the last one indicating the end of the header):
 
 ```http
-GET /status?name=ryan HTTP/1.1\r\n
-Accept: text/plain\r\n
-\r\n
+GET /status?name=ryan HTTP/1.1
+Accept: text/plain
 ```
 
 Then `request.url` will be:

doc/api_assets/README.md

@@ -2,14 +2,15 @@
 
 ## highlight.pack.js
 
-_Generated by [highlightjs.org/download][] on 2020-05-16._
+_Generated by [highlightjs.org/download][] on 2020-06-07._
 
 Grammars included in the custom bundle:
 
 * Bash
 * C
 * C++
 * CoffeeScript
+* HTTP
 * JavaScript
 * JSON
 * Markdown

doc/api_assets/hljs.css

@@ -7,6 +7,7 @@
   color: #333;
 }
 
+.hljs-attribute,
 .hljs-keyword {
   color: #338;
 }