doc: Add godoc to VerifyMembership regarding path (cosmos#1742)

Co-authored-by: Carlos Rodriguez <carlos@interchain.io>

modules/core/23-commitment/types/merkle.go

@@ -129,6 +129,7 @@ func ApplyPrefix(prefix exported.Prefix, path MerklePath) (MerklePath, error) {
 var _ exported.Proof = (*MerkleProof)(nil)
 
 // VerifyMembership verifies the membership of a merkle proof against the given root, path, and value.
+// Note that the path is expected as []string{<store key of module>, <key corresponding to requested value>}.
 func (proof MerkleProof) VerifyMembership(specs []*ics23.ProofSpec, root exported.Root, path exported.Path, value []byte) error {
 	if err := proof.validateVerificationArgs(specs, root); err != nil {
 		return err

modules/core/exported/commitment.go

@@ -35,7 +35,7 @@ type Path interface {
 // Proof implements spec:CommitmentProof.
 // Proof can prove whether the key-value pair is a part of the Root or not.
 // Each proof has designated key-value pair it is able to prove.
-// Proofs includes key but value is provided dynamically at the verification time.
+// Proofs include key but value is provided dynamically at the verification time.
 type Proof interface {
 	VerifyMembership([]*ics23.ProofSpec, Root, Path, []byte) error
 	VerifyNonMembership([]*ics23.ProofSpec, Root, Path) error