Update README.md

[Kyguy0]

"NOTE: the plugin takes selection or" this should say OF not OR

[teran]

Hello @Kyguy0,

First of all thank you for your interest to deduplicator Lightroom plugin.

I've checked the README once again and the logic for file selection and the description is actually looks correct.

Let me describe what does it mean:
Deduplicator for its work takes file selection from Lightroom Library but since there's no option to remove selection from single file (in Lightroom SDK) it assumes the single file selection is the same case when user doesn't select anything which is treated as request to process all the photos.

If the phrase in README makes any doubts for you feel free to suggest the change in PR or let me know how it could be changed but it's not a typo and doesn't meant to be fixed such way.

Thank you for making Deduplicator and its documentation better!