fix: migration issues (#896)

| [![PR App][icn]][demo] | Fix RM-XYZ |
| :--------------------: | :--------: |

## 🧰 Changes

Fixes some issus that come up during testing.

1. Close unclosed self-closing tags.
2. Handle mutli-line html comments.

## 🧬 QA & Testing

- [Broken on production][prod].
- [Working in this PR app][demo].

[demo]: https://markdown-pr-PR_NUMBER.herokuapp.com
[prod]: https://SUBDOMAIN.readme.io
[icn]:
https://user-images.githubusercontent.com/886627/160426047-1bee9488-305a-4145-bb2b-09d8b757d38a.svg

__tests__/compilers/compatability.test.ts

@@ -1,4 +1,5 @@
 import { mdx } from '../../index';
+import * as rdmd from '@readme/markdown-legacy';
 
 describe('compatability with RDMD', () => {
   it('compiles variable nodes', () => {
@@ -51,11 +52,56 @@ describe('compatability with RDMD', () => {
   });
 
   it('compiles html comments to JSX comments', () => {
-    const ast = {
-      type: 'html',
-      value: '<!-- commentable -->',
-    };
+    const md = `
+This is some in progress <!-- commented out stuff -->
+`;
+
+    expect(mdx(rdmd.mdast(md)).trim()).toBe('This is some in progress {/* commented out stuff */}');
+  });
+
+  it('compiles multi-line html comments to JSX comments', () => {
+    const md = `
+## Wip
+
+<!--
+
+### Some stuff I was working on
+
+-->
+`;
+
+    expect(mdx(rdmd.mdast(md)).trim()).toMatchInlineSnapshot(`
+      "## Wip
+
+      {/*
+
+      ### Some stuff I was working on
+
+      */}"
+    `);
+  });
+
+  it('closes un-closed self closing tags', () => {
+    const md = `
+This is a break: <br>
+`;
+
+    expect(mdx(rdmd.mdast(md)).trim()).toBe('This is a break: <br />');
+  });
+
+  it('closes un-closed self closing tags with a space', () => {
+    const md = `
+This is a break: <br >
+`;
+
+    expect(mdx(rdmd.mdast(md)).trim()).toBe('This is a break: <br />');
+  });
+
+  it('closes complex un-closed self closing tags', () => {
+    const md = `
+This is an image: <img src="http://example.com/#\\>" >
+`;
 
-    expect(mdx(ast).trim()).toBe('{/* commentable */}');
+    expect(mdx(rdmd.mdast(md)).trim()).toBe('This is an image: <img src="http://example.com/#\\>" />');
   });
 });