[#674] Add script for generating png files from mmd

variants-doc/generate_png.bash

@@ -0,0 +1,10 @@
+#!/usr/bin/env bash
+
+echo "Installing mermaid-cli"
+npm update -g @mermaid-js/mermaid-cli || echo "Failed to install mermaid-cli. Aborting"
+
+for mmd_file in ./*.mmd; do
+    png_file="${mmd_file%.mmd}.png"
+    echo "- Generating ${png_file} from ${mmd_file}"
+    mmdc --input "${mmd_file}" --output "${png_file}" --theme dark --backgroundColor transparent
+done