From this version, xplr won't annoy the users to visit the upgrade guide
when there is no need.
Also, users will only get upgrade related notification when it is
there is one.
- Rename `custom` field for node metadata to `meta`.
- Move `icon` to `meta.icon`.
- Rename `normal_ui` to `default_ui`.
- Rename `filetypes` to `node_types`.
- Split `modes` into `modes.builtin` and `modes.custom`.
- Add the missing `create file` mode.
- Rename `focused_ui` to `focus_ui`.
- Make `general.table.header` non-nullable.
- Add support for incremental configuration updates.
Ref: https://github.com/sayanarijit/xplr/issues/45
Also be less aggressive for version compatibility.
Use the following logic:
Knowing that we use `{major}.{minor}.{patch}` versioning,
- Major version mismatch are incompatible. Fail with error, suggesting to
visit the Upgrade Guide.
- Minor version updates and patch fixes are compatible. Suggest user to
update the config file version manually. Or visit the Upgrade Guide.
- However, if the config file has greater value for minor version
than the app, also fail with error. Suggesting the user to visit Upgrade
Guide. Though in this case, the user will be downgrading.
Ref: https://github.com/sayanarijit/xplr/issues/45
