feat: add stubs

Author: saitho

project.go

@@ -0,0 +1,11 @@
+package pluginlib
+
+type Project struct {
+	Name string
+}
+
+func GetProject() Project {
+	// mock function
+	// behaviour is implemented in StackHead main repository
+	return Project{}
+}

stackhead.go

@@ -1,6 +1,11 @@
 package pluginlib
 
-func StackHeadExecute(command string) {
+func StackHeadExecute(command string, args interface{}) {
+	// mock function
+	// behaviour is implemented in StackHead main repository
+}
+
+func InstallPackage(packages interface{}) {
 	// mock function
 	// behaviour is implemented in StackHead main repository
 }