add missing "target" parameter in readme

Author: jmalak

README.md

@@ -20,6 +20,7 @@ steps:
 - uses: open-watcom/setup-watcom@v0
   with:
     version: "2.0"
+    target:  "dos"
 - run: |
     wcl386 -zq -d+ -i"${{ env.WATCOM }}/h" -w3 -bt=dos -d2 -fomain.c.obj -c -cc main.c
     wlink option quiet name hello.exe opt map system dos4g debug all file main.c.obj