Create a minimal interactive shell

TODO

@@ -1,8 +1,15 @@
-- Mark all classes as extern(C++) to interface with C++.
-- Some nodes assert(false, "Not implemented") because their logic is handled
-  in the parent nodes. Move this logic to the nodes themselves.
-- Implement multiplication and division.
-- Split tester.cpp into a header and implementation files.
-- The generate function in backend.d contains the whole compilation logic.
-  It's not a backend task.
-- Output assembly.
+- After inserting autocompletion move the cursor to the end of the insertion.
+- Support multiple selections for insertion in fzf.
+- Vi mode.
+- Don't hardcode fzf binary path.
+- Persist the history.
+- Send the word under the cursor to fzf as initial input.
+- Replace hard coded ANSI codes with constants or functions.
+- Show the hostname in the prompt.
+- Crash if the cd directory doesn't exist.
+- Home directory expansion.
+- Paste pastes only the first character.
+- When we read the key and an error occures how it should be handled?
+- Kitty protocol works with UTF8 code points for escape sequences with modifiers.
+  They can be wider than an unsigned char.
+- Add a bar with additional information under the prompt (edit_bar).