fix: hanging dot expressions (#44)

Problem: `token_immediate` broke hanging methods like
```
myobj
  .do_something('now')
```

Solution: remove `token_immediate` again

Author: clason

grammar/operation.js

@@ -84,7 +84,7 @@ module.exports = {
       ),
       repeat1(
         seq(
-          token.immediate("."),
+          ".",
           choice(
             field("function", $.normal_command),
             field("object", $.listitem),

src/grammar.json

@@ -1591,11 +1591,8 @@
             "type": "SEQ",
             "members": [
               {
-                "type": "IMMEDIATE_TOKEN",
-                "content": {
-                  "type": "STRING",
-                  "value": "."
-                }
+                "type": "STRING",
+                "value": "."
               },
               {
                 "type": "CHOICE",