fix: treat a line of only tabs as a blank line between paragraphs (#4007)

Author: sarathfrancis90

src/rules.ts

@@ -128,7 +128,7 @@ const lheadingGfm = edit(lheadingCore)
   .replace(/html/g, / {0,3}<[^\n>]+>\n/) // block html can interrupt
   .replace(/table/g, / {0,3}\|?(?:[:\- ]*\|)+[\:\- ]*\n/) // table can interrupt
   .getRegex();
-const _paragraph = /^([^\n]+(?:\n(?!hr|heading|lheading|blockquote|fences|list|html|table| +\n)[^\n]+)*)/;
+const _paragraph = /^([^\n]+(?:\n(?!hr|heading|lheading|blockquote|fences|list|html|table|[ \t]+\n)[^\n]+)*)/;
 const blockText = /^[^\n]+/;
 const _blockLabel = /(?!\s*\])(?:\\[\s\S]|[^\[\]\\])+/;
 const def = edit(/^ {0,3}\[(label)\]: *(?:\n[ \t]*)?([^<\s][^\s]*|<.*?>)(?:(?: +(?:\n[ \t]*)?| *\n[ \t]*)(title))? *(?:\n+|$)/)

test/specs/new/blank_line_with_tabs.html

@@ -0,0 +1,4 @@
+<p>foo</p>
+<p>bar</p>
+<p>baz</p>
+<p>qux</p>

test/specs/new/blank_line_with_tabs.md

@@ -0,0 +1,10 @@
+---
+gfm: false
+---
+foo
+	
+bar
+
+baz
+	 	
+qux