add fdupes documentation

this is for fdupes: https://github.com/adrianlopezroche/fdupes

pages/common/fdupes.md

@@ -0,0 +1,20 @@
+# fdupes
+
+> Finds duplicate files in a given 
+> set of directories
+
+- search a single directory
+
+`fdupe {{directory}}`
+
+- search multiple directories
+
+`fdupe {{directory1}} {{directory2}}`
+
+- search all directories recursively
+
+`fdupe -r {{directory}}`
+
+- search multiple directories, one recursively
+
+`fdupe {{directory1}} -R {{directory2}}`