Implemented underscore syntax in numbers (#29)

Numscript.g4

@@ -37,7 +37,7 @@ PERCENTAGE_PORTION_LITERAL: [0-9]+ ('.' [0-9]+)? '%';
 STRING: '"' ('\\"' | ~[\r\n"])* '"';
 
 IDENTIFIER: [a-z]+ [a-z_]*;
-NUMBER: MINUS? [0-9]+;
+NUMBER: MINUS? [0-9]+ ('_' [0-9]+)*;
 VARIABLE_NAME: '$' [a-z_]+ [a-z0-9_]*;
 ACCOUNT: '@' [a-zA-Z0-9_-]+ (':' [a-zA-Z0-9_-]+)*;
 ASSET: [A-Z/0-9]+;

internal/parser/__snapshots__/parser_test.snap

@@ -2264,3 +2264,40 @@ parser.Program{
     },
 }
 ---
+
+[TestNumberSyntaxUnderscore - 1]
+parser.Program{
+    Vars:       nil,
+    Statements: {
+        &parser.FnCall{
+            Range: parser.Range{
+                Start: parser.Position{Character:0, Line:1},
+                End:   parser.Position{Character:29, Line:1},
+            },
+            Caller: &parser.FnCallIdentifier{
+                Range: parser.Range{
+                    Start: parser.Position{Character:0, Line:1},
+                    End:   parser.Position{Character:11, Line:1},
+                },
+                Name: "set_tx_meta",
+            },
+            Args: {
+                &parser.StringLiteral{
+                    Range: parser.Range{
+                        Start: parser.Position{Character:12, Line:1},
+                        End:   parser.Position{Character:16, Line:1},
+                    },
+                    String: "k1",
+                },
+                &parser.NumberLiteral{
+                    Range: parser.Range{
+                        Start: parser.Position{Character:18, Line:1},
+                        End:   parser.Position{Character:28, Line:1},
+                    },
+                    Number: 1234567,
+                },
+            },
+        },
+    },
+}
+---