Fix highlighting for metadata attached to memories.

Author: whitequark

examples/memory.uir

@@ -3,7 +3,8 @@
 %2:32 = input "wdata"
 %3:5 = input "raddr"
 %4:1 = input "ren"
-%5:_ = memory depth=#32 width=#32 {
+!123 = source "foo.py" (#0 #0) (#0 #0)
+%5:_ = memory depth=#32 width=#32 !123 {
   init 00000000000000000000000000000000*30
   write addr=%1:5 data=%2:32 mask=11111111111111111111111111111111 clk=%0
   %5:32 = read addr=%3:5 clk=%0 en=%4 [rdfirst]

syntaxes/prjunnamed.tmLanguage.json

@@ -76,6 +76,7 @@
         {"include": "#comment"},
         {"include": "#decimal"},
         {"include": "#ternary"},
+        {"include": "#metadata-ref"},
         {"include": "#cell-ref"},
         {"include": "#cell-ref-new"},
         {"include": "#memory-keyword"}