Add a Plugin Request Template (#392)

Make it easy for users to request a new plugin

Author: Lagoja

.github/ISSUE_TEMPLATE/plugin-request.md

@@ -0,0 +1,20 @@
+---
+name: Plugin Request
+about: Suggest a new Plugin
+title: "[Plugin Request]: <Package Name>"
+labels: plugin request
+assignees: Lagoja
+
+---
+
+** What is the name of the package(s) you are requesting a plugin for?**
+Please use the name as it appears in https://search.nixos.org/packages. 
+
+**Does the package work today?**
+If not, provide a concise explanation of what is going wrong
+
+**[Optional] What configuration would you propose for this plugin?**
+E.g., create a service, environment variables, helper files, etc.
+
+**Additional context**
+Add any other context or screenshots about the feature request here.