fix(markdown): trailing spaces after front matters are allowed (#5107)

```md
---···· <--- allowed
yaml
---···· <--- allowed

markdown
```

src/utils/front-matter.js

@@ -13,14 +13,17 @@ function parse(text) {
     .join("|");
 
   const match = text.match(
-    new RegExp(`^(${delimiterRegex})\\n(?:([\\s\\S]*?)\\n)?\\1(\\n|$)`)
+    // trailing spaces after delimiters are allowed
+    new RegExp(
+      `^(${delimiterRegex})[^\\n\\S]*\\n(?:([\\s\\S]*?)\\n)?\\1[^\\n\\S]*(\\n|$)`
+    )
   );
 
   if (match === null) {
     return { frontMatter: null, content: text };
   }
 
-  const raw = match[0].trimRight();
+  const raw = match[0].replace(/\n$/, "");
   const delimiter = match[1];
   const value = match[2];
 

tests/markdown_yaml/__snapshots__/jsfmt.spec.js.snap

@@ -64,3 +64,22 @@ hello: world
 Content
 
 `;
+
+exports[`trailing-spaces.md - markdown-verify 1`] = `
+---
+           v spaces
+---         
+
+This paragraph should be considered part of the _markdown_ instead of *yaml*.
+
+---
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+---
+v spaces
+---
+
+This paragraph should be considered part of the _markdown_ instead of _yaml_.
+
+---
+
+`;

tests/markdown_yaml/trailing-spaces.md

@@ -0,0 +1,7 @@
+---
+           v spaces
+---         
+
+This paragraph should be considered part of the _markdown_ instead of *yaml*.
+
+---