[input] Put necessary double quotes back

My fault, I removed them in commit 78611457, but they are necessary.
Without them, we are getting the following error when one of the
terminfo[] values is empty:

    init.zsh:14: bad set of key/value pairs for associative array

Fixes #310

modules/input/init.zsh

@@ -17,30 +17,30 @@ key_info=(
   'ControlRight' '\e[1;5C \e[5C \e\e[C \eOc \eOC'
   'Escape'       '\e'
   'Meta'         '\M-'
-  'Backspace'    ${terminfo[kbs]}
-  'BackTab'      ${terminfo[kcbt]}
-  'Left'         ${terminfo[kcub1]}
-  'Down'         ${terminfo[kcud1]}
-  'Right'        ${terminfo[kcuf1]}
-  'Up'           ${terminfo[kcuu1]}
-  'Delete'       ${terminfo[kdch1]}
-  'End'          ${terminfo[kend]}
-  'F1'           ${terminfo[kf1]}
-  'F2'           ${terminfo[kf2]}
-  'F3'           ${terminfo[kf3]}
-  'F4'           ${terminfo[kf4]}
-  'F5'           ${terminfo[kf5]}
-  'F6'           ${terminfo[kf6]}
-  'F7'           ${terminfo[kf7]}
-  'F8'           ${terminfo[kf8]}
-  'F9'           ${terminfo[kf9]}
-  'F10'          ${terminfo[kf10]}
-  'F11'          ${terminfo[kf11]}
-  'F12'          ${terminfo[kf12]}
-  'Home'         ${terminfo[khome]}
-  'Insert'       ${terminfo[kich1]}
-  'PageDown'     ${terminfo[knp]}
-  'PageUp'       ${terminfo[kpp]}
+  'Backspace'    "${terminfo[kbs]}"
+  'BackTab'      "${terminfo[kcbt]}"
+  'Left'         "${terminfo[kcub1]}"
+  'Down'         "${terminfo[kcud1]}"
+  'Right'        "${terminfo[kcuf1]}"
+  'Up'           "${terminfo[kcuu1]}"
+  'Delete'       "${terminfo[kdch1]}"
+  'End'          "${terminfo[kend]}"
+  'F1'           "${terminfo[kf1]}"
+  'F2'           "${terminfo[kf2]}"
+  'F3'           "${terminfo[kf3]}"
+  'F4'           "${terminfo[kf4]}"
+  'F5'           "${terminfo[kf5]}"
+  'F6'           "${terminfo[kf6]}"
+  'F7'           "${terminfo[kf7]}"
+  'F8'           "${terminfo[kf8]}"
+  'F9'           "${terminfo[kf9]}"
+  'F10'          "${terminfo[kf10]}"
+  'F11'          "${terminfo[kf11]}"
+  'F12'          "${terminfo[kf12]}"
+  'Home'         "${terminfo[khome]}"
+  'Insert'       "${terminfo[kich1]}"
+  'PageDown'     "${terminfo[knp]}"
+  'PageUp'       "${terminfo[kpp]}"
 )
 
 # Bind the keys