Updated detection of centos to accept all EL8

installer.sh

@@ -57,7 +57,7 @@ elif [[ "${dist}" == *"debian"* ]] && [[ "${dist_ver}" == *"10"* ]]; then
  PKGI="${PKGM} install -y --no-install-recommends"
  PKGLIST="apt"
  shortdist=deb10
-elif [[ "${dist}" == *"centos"* ]] && [[ "${dist_ver}" == *"8"* ]]; then
+elif [ "$(grep -oP '(?<=^PLATFORM_ID=).+' /etc/os-release | tr -d '"')" = "platform:el8" ]; then
  PKGM="dnf"
  PKGUC="$PKGM check-update --refresh"
  PKGUP="$PKGM update -y"