[soy mode] Add velog tag

Author: axellew

mode/soy/soy.js

@@ -46,6 +46,7 @@
     "delcall": { soyState: "templ-ref" },
     "log": {},
     "element": { variableScope: true },
+    "velog": {},
   };
 
   var indentingTags = Object.keys(tags).filter(function(tag) {

mode/soy/test.js

@@ -308,4 +308,7 @@
 
   MT('import',
    '[keyword import] {[def Name], [variable Person] [keyword as] [def P]} [keyword from] [string \'examples/proto/example.proto\'];');
+
+  MT('velog',
+    '[keyword {velog] [variable-2&error $data][keyword }] Logged [keyword {/velog}]');
 })();