Added MIN_TARGET and MAX_TARGET

EIPS/eip-918.md

@@ -27,6 +27,8 @@ The general behavioral specification includes a primary function that defines th
 
 ``` solidity
 interface ERC918Interface {
+    function MIN_TARGET() external returns (uint256);
+    function MAX_TARGET() external returns (uint256);
     function adjustmentInterval() external returns (uint);
     function challengeNumber() external returns (bytes32);
     function miningTarget() external returns (uint256);
@@ -44,6 +46,20 @@ interface ERC918Interface {
  - The following specifications use syntax from Solidity compiler version `0.4.25`
  - Callers MUST handle `false` from any `returns (bool success)`.  Callers MUST NOT assume that `false` is never returned!
 
+#### MIN_TARGET
+Returns the minimum possible target that the mineable contract will provide as part of the proof of work algorithm.
+
+```solidity
+function MIN_TARGET() external public returns (uint256)
+```
+
+#### MAX_TARGET
+Returns the maximum possible target that the mineable contract will provide as part of the proof of work algorithm.
+
+```solidity
+function MAX_TARGET() external public returns (uint256)
+```
+
 #### blocksPerReadjustment
 Returns the number of block rewards per difficulty readjustment.
 ```solidity