Logic:

1. inside ConfigurationManager2.getConfig
2. if formatter setting useSeparateOnSaveSettings is true then
3. if currently setting onSave is true then
4. if ./ablFormatter/onSaveConfig.json file is present then
5. use this json config as primary config

Basically similar logic to what we have with current setting override feature

Also, we may skip implementing a separate setting useSeparateOnSaveSettings, but in that case we need to read the file once and implement a listener for changes.