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.

README.md

@@ -29,7 +29,7 @@ Simply follow the official guide. <https://aka.ms/LinuxPortal>
 2. Follow the official guide to setup password policy file & disk encryption.
 3. Run `intune-portal` to enroll your machine.
 
-> I don't know how does intune-portal detect your disk encryption settings. Theoretically, dm-crypt (with or without LUKS) + LVM for root partition should be enough.
+> For disk encryption settings, theoretically, dm-crypt (with or without LUKS) + LVM for root partition should be enough.
 
 ## Move certificates from Level-2 machine to Level-1 machine
 
@@ -127,9 +127,9 @@ If getting this problem on ubuntu... I don't know.
 
 - intune-portal crashed after code 1200:
 
-rm -rf ~/.Microsoft ; it will let you login again.
+`rm -rf ~/.Microsoft ~/.cache/intune-portal` and try again.
 
 - couldn't enroll your device. There was an expected error trying to enroll the device.
 
-Terminal shows 400 bad request. I fixed this problem by removing `~/.Microsoft` and `~/.cache/intune-portal`, reinstall intune-portal, and enroll again.
+Terminal shows 400 bad request. I fixed this problem by `rm -rf ~/.Microsoft ~/.cache/intune-portal`, reinstall intune-portal, and enroll again.