Update README.md

README.md

-# filter_media
+# Characterizing Filter media
+
+Masks chatacterized: \
+[3M N95](./3M_N95/README.md) \
+[Gerson N95](./Gerson_N95/readme.md) \
+[Kimberly-Clark 47117](./KC_47117/readme.md)
 
-characterizing filter media 
\ No newline at end of file