Add pausable proposal (solana-labs#1506)

* feat: add pausable proposal

* fix: update proposal

token-swap/proposals/Pausable.md

@@ -0,0 +1,26 @@
+# Pausable & Ownable 
+
+Implement two programs for SPL that can be used to extend contracts with ability to pause, resume and check for the owner before instructions are executed.
+
+An Owner program with the instructions you've listed:
+
+    - set owner
+    - renounce ownership
+    - check owner
+
+Additionally:
+* an Owner struct should contain Option<Pubkey>
+* library code should generate a pda, probably given (struct_key, program_id)
+
+Given an Owner program, compose it with the Pause program.
+
+    - pause
+    - resume
+
+Note: only owner can pause/resume normal operations
+
+For both programs provide example usage from other programs via CPI and unit tests.
+
+Links: 
+* [Pausable solidity contract](https://github.com/OpenZeppelin/openzeppelin-contracts/blob/24a0bc23cfe3fbc76f8f2510b78af1e948ae6651/contracts/security/Pausable.sol)
+* [Ownable solidity contract](https://github.com/OpenZeppelin/openzeppelin-contracts/blob/24a0bc23cfe3fbc76f8f2510b78af1e948ae6651/contracts/access/Ownable.sol)