lichen_rpc: Add a quick README in for iteration purposes

Signed-off-by: Ikey Doherty <[email protected]>

lichen_rpc/README.md

@@ -0,0 +1,26 @@
+# lichen_rpc
+
+This crate contains the `lichen_rpc` executable, a helper backend for the lichen
+installer that communicates using the [varlink](https://varlink.org) protocol over
+a local UNIX socket.
+
+It is intended to be launched by a compatible frontend via some escalation system, such
+as `pkexec` or `sudo`, ensuring that the frontend can communicate with the backend without
+running as root itself.
+
+It is in a very early stage, but eventually will be the entire backend of our installer.
+
+## Testing
+
+First, launch the backend:
+
+```sh
+pkexec ./target/debug/lichen_rpc --varlink=unix:@testinglichen
+```
+
+Then, in another terminal, run the [varlink cli](https://crates.io/crates/varlink-cli)
+
+```sh
+varlink call unix:@testinglichen/com.serpentos.lichen.disks.GetDisks
+varlink call unix:@testinglichen/com.serpentos.lichen.disks.GetPartitions '{"disk": "/dev/sda"}'
+```