Change a link to an autolink in How to write in Markdown (#31435)

* Change a link to a autolink in `How to write in Markdown`

* Add missing period

* Remove double "and"

files/en-us/mdn/writing_guidelines/howto/markdown_in_mdn/index.md

@@ -10,13 +10,13 @@ This page describes how we use Markdown to write documentation on MDN Web Docs.
 
 ## Baseline: GitHub-Flavored Markdown
 
-The baseline for MDN Markdown is GitHub-Flavored Markdown (GFM): <https://github.github.com/gfm/>. This means that you can refer to the GFM specification for anything not explicitly specified in this page. GFM in turn is a superset of CommonMark ([https://spec.commonmark.org/](https://spec.commonmark.org/)).
+The baseline for MDN Markdown is GitHub-Flavored Markdown (GFM): <https://github.github.com/gfm/>. This means that you can refer to the GFM specification for anything not explicitly specified in this page. GFM in turn is a superset of CommonMark (<https://spec.commonmark.org/>).
 
 ## Links
 
 The GFM specification defines two basic types of links:
 
-- [inline links](https://github.github.com/gfm/#inline-link), in which the destination is given immediately after the link text
+- [inline links](https://github.github.com/gfm/#inline-link), in which the destination is given immediately after the link text.
 - [reference links](https://github.github.com/gfm/#reference-link), in which the destination is defined elsewhere in the document.
 
 On MDN we allow only inline links.
@@ -477,7 +477,7 @@ The main limitations of GFM table syntax are:
 - GFM tables may not have a header column.
 - GFM won't parse GFM block elements in table cells. For example, you can't have a list in a table cell.
 - GFM tables cannot have classes assigned to them.
-- GFM doesn't support any table elements beyond `<table>`, `<tr>`, and `<th>`, and `<td>`.
+- GFM doesn't support any table elements beyond `<table>`, `<tr>`, `<th>`, and `<td>`.
 - GFM doesn't support any table element attributes like `colspan`, `rowspan`, or `scope`.
 
 If an author needs to use any of the unsupported features, they should write the table in HTML.