Support multi-letter uppercase sigils (#50)

Author: jonatanklosko

grammar.js

@@ -334,7 +334,7 @@ module.exports = grammar({
             )
           ),
           seq(
-            alias(token.immediate(/[A-Z]/), $.sigil_name),
+            alias(token.immediate(/[A-Z]+/), $.sigil_name),
             choice(
               $._quoted_double,
               $._quoted_single,

test/corpus/expression/sigil.txt

@@ -189,6 +189,19 @@ upper sigil / escape terminator
     (escape_sequence)
     (quoted_content)))
 
+=====================================
+upper sigil / multiple characters
+=====================================
+
+~MAT"1 2"
+
+---
+
+(source
+  (sigil
+    (sigil_name)
+    (quoted_content)))
+
 =====================================
 heredoc delimiter
 =====================================