Added documentation for compute_shuffled_index.

Added correct json input for compute_shuffled_index circuit in example.
Clone test input data if needed.

vendor/zkllvm-metacraft-circuits/docs/compute_shuffled_index.md

@@ -0,0 +1,17 @@
+# Compute shuffled index documentation.
+
+### *Implementation*
+   The implementation code of the circuit is under "DendrETH/vendor/zkllvm-metacraft-circuits/src/circuits_impl/". 
+   This code is used in both the compilation as circuit and as executable.
+
+### *Circuit build*
+   In order to build as circuit, we need an entry point marked with the `[[circuit]]` directive. This is done through a wrapper 
+   that uses the implementation code and resides in "DendrETH/vendor/zkllvm-metacraft-circuits/src/circuits". Since currently the Crypto3
+   library does not implement computation of sha256 on a byte buffer, we use a header only library for the sha256 computations, which has 
+   negative performance consequences.
+
+### *Executable build + tests*
+   The implementation code of the circuit is compiled as executable and tested against the input data from 
+   https://github.com/ethereum/consensus-spec-tests.git. The tests reside in "DendrETH/vendor/zkllvm-metacraft-circuits/src/tests/compute_shuffled_index_test/".
+   For convenience, we have a script that performs all necessary steps to run the test -> "DendrETH/vendor/zkllvm-metacraft-circuits/scripts/compile_and_run_tests.sh".
+   It is required that docker is installed on the machine that will run the tests.

vendor/zkllvm-metacraft-circuits/scripts/compile_and_run_tests.sh

@@ -14,6 +14,11 @@ then
     git clone git@github.com:metacraft-labs/finalizer-data.git $SCRIPT_DIR/../src/tests/verify_attestation_data_test/finalizer-data
 fi
 
+if [ ! -d $SCRIPT_DIR/../../consensus-spec-tests ]
+then 
+    git clone git@github.com:ethereum/consensus-spec-tests.git $SCRIPT_DIR/../../consensus-spec-tests
+fi
+
 cd $CURRENT_DIR
 
 COMMAND='cmake -G "Unix Makefiles" -B ${ZKLLVM_BUILD:-build} -DCMAKE_BUILD_TYPE=Release -DCMAKE_CXX_COMPILER=g++ . && make -C ${ZKLLVM_BUILD:-build} template'