Update README.md

[nida]

Adding Nife.io details

Requirements

• [x] This is Software as a Service not self hosted
• [x] It has a free tier not just a free trial
• [x] The submission mentions what is free
• [x] The submission is not already present in the list
• [x] The service has contact details of those running it and a privacy policy

[nida]

Adding Nife.io free tier details