Add Usage section to README.md #681

1. 
   jonasnick commented at 9:52 am on October 29, 2019: contributor

   Could provide examples for pubkey generation, signing and verification and add a link to the include files for more documentation.
2. 
   jonasnick commented at 8:30 am on April 28, 2020: contributor

   Duplicate of #184
3. jonasnick marked this as duplicate on Apr 28, 2020
4. jonasnick closed this on Apr 28, 2020

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jonasnick