Typo "susbstition" in PAL manual 4z3964

Just reporting a minor typo for the PAL team.

See: https://portableapps.crackfree.org/manuals/portableapps.crackfree.orgLauncher/ref/envsub.html

There's a typo in the page title and the intro paragraph. The title typo is replicated throughout the manual (table of contents, index, nav bar, etc).