Allow a space after {{

Author: Mpdreamz

src/Elastic.Markdown/Myst/InlineParsers/Substitution/SubstitutionParser.cs

@@ -176,7 +176,7 @@ public override bool Match(InlineProcessor processor, ref StringSlice slice)
 		startPosition -= openSticks;
 		startPosition = Math.Max(startPosition, 0);
 
-		var key = content.ToString().Trim(['{', '}']).ToLowerInvariant();
+		var key = content.ToString().Trim(['{', '}']).Trim().ToLowerInvariant();
 		var found = false;
 		var replacement = string.Empty;
 		var components = key.Split('|');

tests/authoring/Inline/Substitutions.fs

@@ -46,6 +46,7 @@ The following should be subbed: {{hello-world}}
 not a comment
 not a {{valid-key}}
 not a {substitution}
+The following should be subbed too: {{ hello-world }}
 """
 
     [<Fact>]
@@ -58,5 +59,7 @@ not a {substitution}
  <p>The following should be subbed: Hello World!
  	not a comment
  	not a {{valid-key}}
- 	not a {substitution}</p>
+ 	not a {substitution}
+    The following should be subbed too: Hello World!
+ 	</p>
 """