Change README extension to md #32

Signed-off-by: Jono Yang <jyang@nexb.com>

Author: JonoYang

README.rst README.mdREADME.rst renamed to README.md

@@ -6,7 +6,7 @@
 
 **purl-validator** is a Rust library for validating [Package URLs (PURLs)](https://github.com/package-url/purl-spec). It works fully offline, including in **air-gapped** or **restricted environments**, and answers one key question: **Does the package this PURL represents actually exist?**
 
-## How It Works?
+## How Does It Work?
 
 **purl-validator** is shipped with a pre-built FST (Finite State Transducer), a set of compact automata containing latest Package URLs mined by the MineCode[^1]. Library uses this FST to perform lookups and confirm whether the **base PURL**[^2] exists.