- Added diagram for global context manager (GCM) structure.
- Removed local func@get_ctx_head (unused).
- Updated func@M.update:
- function takes 2 parameter arguments (see docstring).
- constructs new record for the given context in the GCM to keep
record of a newly constructed window buffer.
- function updates the GCM with the new record.
- Updated func@M.flush:
- handles for new structure of records in the GCM.
- see docstring for info.
Added a context manager for handling and managing windows/buffers
constructed by built-ins. This was handled by the `new()` function in
presser/init.lua but is now a dedicated module.
