Add custom app example

custom_app/docker-bake.hcl

@@ -0,0 +1,25 @@
+APP_NAME="custom_app"
+
+variable "FRAPPE_VERSION" {}
+
+group "default" {
+    targets = ["backend", "frontend"]
+}
+
+target "backend" {
+    dockerfile = "backend.Dockerfile"
+    tags = ["custom_app/worker:latest"]
+    args = {
+      "FRAPPE_VERSION" = FRAPPE_VERSION
+      "APP_NAME" = APP_NAME
+    }
+}
+
+target "frontend" {
+    dockerfile = "frontend.Dockerfile"
+    tags = ["custom_app/nginx:latest"]
+    args = {
+      "FRAPPE_VERSION" = FRAPPE_VERSION
+      "APP_NAME" = APP_NAME
+    }
+}