[session][workstation] Add config file for root session

This adds a configuration file for workstation to specify its root
session.

Change-Id: I1d425812d313c30e0b551d0706c0a2f3bac2a280
diff --git a/session_shells/ermine/session/BUILD.gn b/session_shells/ermine/session/BUILD.gn
index c6c33a0..7ed67ea 100644
--- a/session_shells/ermine/session/BUILD.gn
+++ b/session_shells/ermine/session/BUILD.gn
@@ -4,6 +4,7 @@
 
 import("//build/package.gni")
 import("//build/rust/rustc_binary.gni")
+import("//src/session/build/session_config.gni")
 
 rustc_binary("bin") {
   name = "workstation_session"
@@ -19,9 +20,9 @@
     "//sdk/fidl/fuchsia.ui.policy:fuchsia.ui.policy-rustc",
     "//sdk/fidl/fuchsia.ui.scenic:fuchsia.ui.scenic-rustc",
     "//sdk/fidl/fuchsia.ui.views:fuchsia.ui.views-rustc",
+    "//src/lib/fidl/rust/fidl",
     "//src/lib/fuchsia-async",
     "//src/lib/fuchsia-component",
-    "//src/lib/fidl/rust/fidl",
     "//src/lib/syslog/rust:syslog",
     "//src/lib/ui/fuchsia-scenic",
     "//src/lib/ui/input-synthesis",
@@ -49,4 +50,8 @@
       name = "workstation_session"
     },
   ]
-}
\ No newline at end of file
+}
+
+session_config("session_config") {
+  config = "//src/experiences/session_shells/ermine/session/session_config.json"
+}
diff --git a/session_shells/ermine/session/session_config.json b/session_shells/ermine/session/session_config.json
new file mode 100644
index 0000000..0d2e14c
--- /dev/null
+++ b/session_shells/ermine/session/session_config.json
@@ -0,0 +1,3 @@
+{
+  "session_url": "fuchsia-pkg://fuchsia.com/workstation_session#meta/workstation_session.cm"
+}
\ No newline at end of file