initramfs hook for tailscale

This is intended to be used with an ephemeral auth key with an ACL tag,
and ACL rules that restrict the ephemeral node to inbound-only traffic.
It does not share instance state with tailscale running in Linux.

Reference:
- https://tailscale.com/kb/1111/ephemeral-nodes/
- https://tailscale.com/kb/1068/acl-tags/#generate-an-auth-key-with-an-acl-tag
- https://tailscale.com/kb/1068/acl-tags/#using-tags-in-acls-for-access-control

debian/changelog

@@ -0,0 +1,5 @@
+tailscale-initramfs (0.1) unstable; urgency=medium
+
+  * Initial Release.
+
+ -- Paul Aurich <paul@darkrain42.org>  Fri, 14 Jan 2022 21:03:16 -0800