adds changelog

Changelog.md

+# CHANGELOG
+
+Changelog format to use:
+
+```
+YYYY-MM-DD  John Doe
+
+    * Big Change 1:
+        <reasoning here>
+    * Another Change 2:
+        <reasoning here>
+```
+---
+
+2021-03-16  Manavalan Gajapathy
+
+    * Creates QuaC workflow, which can run somalier, mosdepth, indexcov, covviz and verifybamid2
+    * Uses pedigree file as input
+    * Makes it production ready.