Add configuration possibility and add option to disable file link title previews

[f4z3r]

Changes

• Update the modules providing the individual functions to accept configuration options.
• Add configuration option to disable title previews in insert_file_link function.
• Update changelog for unreleased features.
• Update Readme for configuration documentation.

Fixes: #59

Notes

I am aware that the way the configuration is passed to the functions is pretty ugly. I am just not aware how to do this nicely with the functions all being returned directly from the modules. What would be cleaner IMO but would require larger changes:

1. Update module structure such that the functions are not directly returned as modules.
2. Enable configuration of individual functions as they are called in the neorg module.

This is mostly needed because the module.config.public table needs to be passed to the called function only when that function is being called (hence the extra function wrappers in module.public.<func> otherwise the user's configuration override is not taken into account, and the defaults set in the same file will always apply.

[max397574]

thank you for your investigations on what the original problem was