Support ArchLinux level-2 enroll; Add intune-portal pkg; Add instructions & FAQ

This PR adds necessary package & instructions to support level-2 enrollment on ArchLinux. Manjaro Linux is still pending for testing.

intune-portal/PKGBUILD

+# Maintainer: Recolic K <root@recolic.net>
+
+https://packages.microsoft.com/ubuntu/20.04/prod/pool/main/i/intune-portal/intune-portal_1.2310.8_amd64.deb
+pkgname=intune-portal
+pkgver=1.2310.8
+pkgrel=0
+pkgdesc="Microsoft Intune helps organizations manage access to corporate apps, data, and resources."
+url="https://packages.microsoft.com/ubuntu/20.04/prod/pool/main/i/intune-portal"
+license=("GPL2")
+arch=("x86_64")
+# Depends: libsoup2.4-1 (>= 2.4.0), libgtk-3-0 (>= 3.21.4), msalsdk-dbusclient (>= 1.0), libssl1.1 (>= 1.1.0), libcurl4 (>= 7.16.2), libc6 (>= 2.29), libsystemd0, libdbus-1-3 (>= 1.9.14), zlib1g (>= 1:1.2.0), libatk1.0-0 (>= 1.12.4), libuuid1 (>= 2.16), libglib2.0-0 (>= 2.35.8), libpam-pwquality (>= 1.4.0-2), gnome-keyring (>= 3.36), libgtk-3-0 (>= 3.9.10), libx11-6, libjavascriptcoregtk-4.0-18, libpango-1.0-0 (>= 1.14.0), libc6 (>= 2.28), libwebkit2gtk-4.0-37 (>= 2.5.3), libsecret-1-0 (>= 0.7), libglib2.0-0 (>= 2.12.0), libpam0g (>= 0.99.7.1), libstdc++6 (>= 9), libsqlite3-0 (>= 3.7.14)
+depends=("glibc>=2.14" "gcc-libs>=3.0" "systemd-libs>=243" "libsdbus-c++0" "microsoft-identity-broker>=1.0")
+makedepends=()
+conflicts=()
+replaces=()
+backup=()
+source=("source.deb::$url/${pkgname}_${pkgver}_amd64.deb")
+validpgpkeys=("")
+sha256sums=("001d0903f26b78a705f36f278df584d9126a7feafc91a70810e814c60460842a")
+install=x.install
+
+package() {
+  cd "$srcdir"
+  ar x source.deb
+  tar xvzf data.tar.gz
+  cp -r "$srcdir/usr" "$pkgdir/"
+}
+
+