Improve Collider tag docs;

api/lovr/physics/Collider/getTag.lua

@@ -5,7 +5,7 @@ return {
   returns = {
     tag = {
       type = 'string',
-      description = 'The Collider\'s collision tag.'
+      description = 'The Collider\'s collision tag, or `nil` if the Collider doesn\'t have a tag.'
     }
   },
   variants = {

api/lovr/physics/Collider/setTag.lua

@@ -12,6 +12,11 @@ return {
     {
       arguments = { 'tag' },
       returns = {}
+    },
+    {
+      description = 'Clear the Collider\'s tag.'
+      arguments = {},
+      returns = {}
     }
   },
   notes = [[