add users/grawity.json

Override the API-provided data, additionally setting format=txt (because
after all these years Inconsolata still cannot render my name right).

users/grawity.json

@@ -0,0 +1,6 @@
+{
+ "copyright": "Mantas Mikulėnas",
+ "email": "grawity@gmail.com",
+ "url": "http://nullroute.eu.org/~grawity/",
+ "format": "txt"
+}