fix(markdown_style): Escape content string (#427)

Author: jouderianjr

src/components/github-style.js

@@ -495,7 +495,7 @@ export default `
       .markdown-body code::before,
       .markdown-body code::after {
         letter-spacing: -0.2em;
-        content: "\00a0";
+        content: "\\00a0";
       }
       .markdown-body pre {
         word-wrap: normal;