enh(csharp) add keywords record and init (C# 9.0)

CHANGES.md

@@ -10,12 +10,14 @@ Big picture:
 
 Language Improvements:
 
+- enh(csharp) Add `init` and `record` keywords for C# 9.0 (#2660) [Youssef Victor][]
 - enh(matlab) Add new R2019b `arguments` keyword and fix `enumeration` keyword (#2619) [Andrew Janke][]
 - fix(kotlin) Remove very old keywords and update example code (#2623) [kageru][]
 - fix(night) Prevent object prototypes method values from being returned in `getLanguage` (#2636) [night][]
 - enh(java) Add support for `enum`, which will identify as a `class` now (#2643) [ezksd][]
 - enh(nsis) Add support for NSIS 3.06 commands (#2653) [idleberg][]
 
+[Youssef Victor]: https://github.com/Youssef1313
 [Josh Goebel]: https://github.com/yyyc514
 [Andrew Janke]: https://github.com/apjanke
 [Samia Ali]: https://github.com/samiaab1990

src/languages/csharp.js

@@ -13,7 +13,7 @@ export default function(hljs) {
       // Normal keywords.
       'abstract as base bool break byte case catch char checked const continue decimal ' +
       'default delegate do double enum event explicit extern finally fixed float ' +
-      'for foreach goto if implicit in int interface internal is lock long ' +
+      'for foreach goto if implicit in init int interface internal is lock long ' +
       'object operator out override params private protected public readonly ref sbyte ' +
       'sealed short sizeof stackalloc static string struct switch this try typeof ' +
       'uint ulong unchecked unsafe ushort using virtual void volatile while ' +
@@ -164,6 +164,16 @@ export default function(hljs) {
           hljs.C_BLOCK_COMMENT_MODE
         ]
       },
+      {
+        beginKeywords: 'record', end: /[{;=]/,
+        illegal: /[^\s:]/,
+        contains: [
+          TITLE_MODE,
+          GENERIC_MODIFIER,
+          hljs.C_LINE_COMMENT_MODE,
+          hljs.C_BLOCK_COMMENT_MODE
+        ]
+      },
       {
         // [Attributes("")]
         className: 'meta',

test/markup/csharp/records.expect.txt

@@ -0,0 +1,4 @@
+<span class="hljs-keyword">public</span> <span class="hljs-keyword">record</span> <span class="hljs-title">MyRecord</span>
+{
+    <span class="hljs-keyword">public</span> <span class="hljs-keyword">string</span> SomeMember { <span class="hljs-keyword">get</span>; <span class="hljs-keyword">set</span>; }
+}

test/markup/csharp/records.txt

@@ -0,0 +1,4 @@
+public record MyRecord
+{
+    public string SomeMember { get; set; }
+}