feat: install east in dev

spack-environment/dev/spack.yaml

@@ -18,6 +18,7 @@ spack:
     - dawncut
     - dd4hep
     - dpmjet
+    - east
     - edm4eic
     - edm4hep
     - eic-smear

spack-environment/packages.yaml

@@ -70,6 +70,9 @@ packages:
   dpmjet:
     require:
     - '@19.3.5'
+  east:
+    require:
+    - '@656aa3192b097a631ddd1e0380e80c26fd6644a7=main'
   edm4eic:
     require:
     - '@2.0.0'