add an option to disable mermaid

[PinkD]

always adding mermaid js file into template makes the generated html file bigger than 1MB

vscode-markdown-pdf/template/template.html

Lines 7 to 9 in 4815dcc

	<script>
	{{{mermaid}}}
	</script>

[yzane]

Please upgrade Markdown PDF to ver1.4.4 and try.

[vowstar]

This change makes it impossible to use offline. It would be better if there is an option for offline use.