Add examples for hashing with sha256 and blake3

miden/examples/hashing/blake3/blake3.inputs

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+{
+    "operand_stack": ["4294967295", "4294967295", "4294967295", "4294967295", "4294967295", "4294967295", "4294967295", "4294967295", "4294967295", "4294967295", "4294967295", "4294967295", "4294967295", "4294967295", "4294967295", "4294967295"]
+}

miden/examples/hashing/blake3/blake3.masm

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+use.std::crypto::hashes::blake3
+
+begin
+    # hash_2to1 pops top 16 elements (64 bytes) from the stack, compute their hash and puts the 
+    # resulting 8 elements (32 bytes) back to the stack.
+    exec.blake3::hash_2to1
+
+    # Check the correctness of the hashing result by comparing it with precomputed correct values. 
+    # This hash is a result of applying a blake3 hashing function to the binary value consisting of
+    # only ones.
+    push.0xD9696D27.0xF209D66E.0xD0DFDEB9.0x7D5992E2.0x44DDA9CB.0xD6FFB5E5.0x8CD0CAA6.0xF0270FA9
+
+    # compare results
+    movupw.2
+    assert_eqw
+    assert_eqw
+end

miden/examples/hashing/sha256/sha256.inputs

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+{
+    "operand_stack": ["4294967295", "4294967295", "4294967295", "4294967295", "4294967295", "4294967295", "4294967295", "4294967295", "4294967295", "4294967295", "4294967295", "4294967295", "4294967295", "4294967295", "4294967295", "4294967295"]
+}

miden/examples/hashing/sha256/sha256.masm

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+use.std::crypto::hashes::sha256
+
+begin
+    # hash_2to1 pops top 16 elements (64 bytes) from the stack, compute their hash and puts the 
+    # resulting 8 elements (32 bytes) back to the stack.
+    exec.sha256::hash_2to1
+
+    # Check the correctness of the hashing result by comparing it with precomputed correct values. 
+    # This hash is a result of applying a sha256 hashing function to the binary value consisting of
+    # only ones.
+    push.0x85E1D1F7.0x8643E4A2.0x2DAD7274.0x1F764AAD.0xBA3EEB20.0xF1D30600.0x294E9E0D.0x8667E718
+
+    # compare results
+    movupw.2
+    assert_eqw
+    assert_eqw
+end