Accept txt for Markdown Preview
Accept txt for Markdown Preview

Amended to accept txt as Markdown Preview. (Kirby CMS uses txt for site content in optional Markdown)
albertinad/MarkdownPreview,CamTosh/MarkdownPreview,gruehle/MarkdownPreview,pl86/MarkdownPreview,albertinad/MarkdownPreview,pl86/MarkdownPreview,CamTosh/MarkdownPreview,gruehle/MarkdownPreview