Add gopher-ls and hddtemp-info @usage, adapted from Toni Ruotto.

scripts/gopher-ls.nse

@@ -3,6 +3,9 @@ Lists files and directories at the root of a gopher service.
 ]]
 
 ---
+-- @usage
+-- nmap -p 70 --script gopher-ls --script-args gopher-ls.maxfiles=100 <target>
+--
 -- @output
 -- 70/tcp open  gopher
 -- | gopher-ls:

scripts/hddtemp-info.nse

@@ -3,6 +3,9 @@ Reads hard disk information (such as brand, model, and sometimes temperature) fr
 ]]
 
 ---
+-- @usage
+-- nmap -p 7634 -sV -sC <target>
+--
 -- @output
 -- 7634/tcp open  hddtemp
 -- |_hddtemp-info: /dev/sda: WDC WD2500JS-60MHB1: 38 C