setting a min version for exported libraries

Author: aalavandhan

contracts/lib/SafeMathInt.sol

@@ -24,7 +24,7 @@ SOFTWARE.
 */
 
 // SPDX-License-Identifier: GPL-3.0-or-later
-pragma solidity 0.8.4;
+pragma solidity ^0.8.4;
 
 /**
  * @title SafeMathInt

contracts/lib/Select.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: GPL-3.0-or-later
-pragma solidity 0.8.4;
+pragma solidity ^0.8.4;
 
 /**
  * @title Select

contracts/lib/UInt256Lib.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: GPL-3.0-or-later
-pragma solidity 0.8.4;
+pragma solidity ^0.8.4;
 
 /**
  * @title Various utilities useful for uint256.