block, vm -> release: README updates from review

Co-authored-by: Ryan Ghods <[email protected]>

Author: holgerd77

packages/block/README.md

@@ -74,7 +74,9 @@ console.log(common.consensusAlgorithm()) // 'ethash'
 const block = Block.fromBlockData({}, { common })
 ```
 
-TODO
+To validate that the difficulty of the block matches the canonical difficulty use `block.validate(blockchain)`.
+
+To calculate the difficulty when creating the block pass in the block option `calcDifficultyFromHeader` with the preceding (parent) `BlockHeader`.
 
 ## Clique/PoA (since v3.1.0)
 

packages/vm/README.md

@@ -81,7 +81,7 @@ Starting with `v5.1.0` the VM supports running both `Ethash/PoW` and `Clique/PoA
 
 ### Ethash/PoW Chains
 
-TODO
+`@ethereumjs/blockchain` validates the PoW algorithm with `@ethereumjs/ethash` and validates blocks' difficulty to match their canonical difficulty.
 
 ### Clique/PoA Chains