docs: add token vesting section

Author: dr497

docs/src/token.md

@@ -861,3 +861,13 @@ the maximum allowed transaction size, remove those extra clean up instructions.
 They can be cleaned up during the next send operation.
 
 The `spl-token gc` command provides an example implementation of this cleanup process.
+
+
+### Token Vesting Contract:
+This program allows you to lock arbitrary SPL tokens and release the locked tokens with a determined unlock schedule. An `unlock schedule` is made of a `unix timestamp` and a token `amount`, when initializing a vesting contract, the creator can pass an array of `unlock schedule` with an arbitrary size giving the creator of the contract complete control of how the tokens unlock over time. 
+
+Unlocking works by pushing a permissionless crank on the contract that moves the tokens to the pre-specified address. The recipient address of a vesting contract can be modified by the owner of the current recipient key, meaning that vesting contract locked tokens can be traded.
+
+- Code: [https://github.com/Bonfida/token-vesting](https://github.com/Bonfida/token-vesting)
+- UI: [https://vesting.bonfida.com/#/](https://vesting.bonfida.com/#/)
+- Audit: The audit was conducted by Kudelski, the report can be found [here](https://github.com/Bonfida/token-vesting/blob/master/audit/Bonfida_SecurityAssessment_Vesting_Final050521.pdf)