docs: add example bindings for uppercasing and lowercasing a word

(The diff looks weird in 'less' -- the "c" before the "^T" hides
two escape sequences.)

doc/sample.nanorc.in

@@ -265,6 +265,12 @@
 ## <Ctrl+Backspace> delete the word to the left of the cursor with:
 # bind ^H chopwordleft main
 
+## For quickly uppercasing or lowercasing the word under the cursor.
+## (These effectively do a Ctrl+Right followed by a Shift+Ctrl+Left,
+## and then pipe the selected text through a sed command.)
+#bind Sh-M-U "Oc|sed 's/.*/\U&/'
+" main
+#bind Sh-M-L "Oc|sed 's/.*/\L&/'
 " main
 
 ## If you would like nano to have keybindings that are more "usual",