Add header to `wget` & add example

sheets/wget

@@ -1,6 +1,12 @@
-# Quietly download a file, continuing where it left of, if the connection fails.
-# Note that the file will be downloaded to the current working directory.
+# wget
+# The non-interactive network downloader
+
+# Quietly download a file, continuing where it left of, if the connection
+# fails. The file will be downloaded to the current working directory.
 wget -qc [URL]
 
 # Specify a location to download the given file.
 wget -qcO [PATH] [URL]
+
+# Download URL using the user agent string provided to the `-U` flag.
+wget -U 'Mozilla/5.0' [URL]