docs: Add template file 'sample mermaid diagram.md'

Author: claremacrae

docs/_meta/templates/sample mermaid diagram.md

@@ -0,0 +1,19 @@
+```mermaid
+flowchart LR
+1[Input Data]
+2[Updated Code]
+3{Output the same?}
+1 --> 2
+2 --> 3
+
+4[Pass]
+3---|Yes|4
+linkStyle 2 stroke:green
+
+5[Fail]
+6[Open diff tool to show changes]
+3---|No|5
+5 --> 6
+
+linkStyle 3 stroke:red
+```