Add document/absolute_path_migrate_me_to_uri (#122)

This fixes an error returned when this value is missing:

```
{"code":"unknown","message":"no absolute path"}
```

Author: avdv

codeium.el

@@ -317,6 +317,9 @@
     "according to https://www.reddit.com/r/emacs/comments/5b7o9r/elisp_how_to_concat_newline_into_string_regarding/
     this can be always \\n")
 
+(codeium-def codeium/document/absolute_path_migrate_me_to_uri ()
+    (or buffer-file-name (expand-file-name (buffer-name))))
+
 (codeium-def codeium/editor_options/tab_size ()
     tab-width)
 (codeium-def codeium/editor_options/insert_spaces ()