alphabet-compliance: Update the README

BUG=b/196055702
TEST=None
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Change-Id: I2a38bd2d613918246b2ee81e0dc7ebf949ed22a7
(cherry picked from commit c39cf0620c3f70ce27915985e9f7bed06dd1a9fd)
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 # Compliance Scripts for Container-Optimized OS
 These are experimental scripts developed for Alphabet compliance.
+The sections referred on the scripts are from [CIS Distribution Independent Linux Benchmark v2.0.0](https://www.cisecurity.org/benchmark/distribution_independent_linux/)