Adding issue template

.github/ISSUE_TEMPLATE/pml1_figure.md

@@ -0,0 +1,15 @@
+---
+name: PML1 figure code
+about: Use this template to specify a figure a code example is needed for
+title: [language] code for PML1 figure [figure-number]
+---
+
+<!--
+Substitute the `[language]` and `[figure-number]` placeholders in issue title for respectively 
+the language the code to create the figure will be written in and the figure number in the 
+format `[chapter].[figure]`. 
+
+Assign the issue to yourself if you are planning on working on this figure code.
+
+The body of the issue can be left empty.
+-->