cmd/sketch: add mount flag for container volumes

Add a mount flag that simplifies mounting host directories into the container.
When specified with format /path/on/host:/path/in/container it's automatically
converted to a docker volume mount argument (-v) in the docker invocation.
This simplifies volume mounting compared to the more generic docker-args flag.

Co-Authored-By: sketch <hello@sketch.dev>
Change-ID: s67251d45fd28831ek
diff --git a/dockerimg/dockerimg.go b/dockerimg/dockerimg.go
index a6d012e..4b50ae1 100644
--- a/dockerimg/dockerimg.go
+++ b/dockerimg/dockerimg.go
@@ -99,6 +99,9 @@
 	// DockerArgs are additional arguments to pass to the docker create command
 	DockerArgs string
 
+	// Mounts specifies volumes to mount in the container in format /path/on/host:/path/in/container
+	Mounts []string
+
 	// ExperimentFlag contains the experimental features to enable
 	ExperimentFlag string
 
@@ -484,6 +487,13 @@
 	}
 	// colima does this by default, but Linux docker seems to need this set explicitly
 	cmdArgs = append(cmdArgs, "--add-host", "host.docker.internal:host-gateway")
+
+	// Add volume mounts if specified
+	for _, mount := range config.Mounts {
+		if mount != "" {
+			cmdArgs = append(cmdArgs, "-v", mount)
+		}
+	}
 	cmdArgs = append(
 		cmdArgs,
 		imgName,