Added acl notes to the knowledge base

knowledge base/acl.md

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+# Access Control Lists assignment
+
+## TL;DR
+
+```shell
+# show acls of file test/declarations.h
+getfacl test/declarations.h
+
+# set permissions for user awe-user
+setfacl -m u:awe-user:rwx test/declarations.h
+
+# set permissions for group awe-group
+setfacl -m "g:awe-group:r-x" test/declarations.h
+
+# make children files and directories inherit acls
+# sets default acls
+setfacl -d -m u:dummy:rw test
+
+# remove a specific acl
+setfacl -x u:dummy:rw test
+
+# remove all acls
+setfacl -b test/declarations.h
+```
+
+## Sources
+
+- [Access Control Lists (ACL) in Linux]
+
+[access control lists (acl) in linux]: https://www.geeksforgeeks.org/access-control-listsacl-linux/