.github: enable md047 (single newline) (#648)

ran-huang · web-flow · commit 2768a924ade6 · 2021-08-26T17:49:22.000+08:00
Signed-off-by: Ran &lt;huangran@pingcap.com&gt;
diff --git a/.github/markdownlint.yml b/.github/markdownlint.yml
@@ -63,3 +63,6 @@ no-alt-text: true
 # MD046
 code-block-style:
   style: fenced
+
+# MD047 - File should end with a single newline character
+single-trailing-newline: true
