add readme

README.md

@@ -0,0 +1,13 @@
+usage
+
+```shell
+#
+# build && install yosys
+DEBIAN_FRONTEND=noninteractive apt-get -y install --no-install-recommends build-essential clang bison flex libreadline-dev gawk tcl-dev libffi-dev git graphviz xdot pkg-config python3 libboost-system-dev libboost-python-dev libboost-filesystem-dev zlib1g-dev ca-certificates gcc iverilog
+cd yosys
+make
+sudo make install
+cd ..
+# run yosys
+bash ./synth.sh | tee ./result/gcd.log
+```