Share Extension: some markdown from Bear is not converted

[designsimply]

Steps to reproduce:

1. Enable Markdown for a WordPress.com blog.
2. Open Bear and add the sample content from below.
3. Tap the (i) icon at top right.
4. Select TXT.
5. Tap the share icon at top right.
6. Select the WordPress app (must be 12.1+).
7. Tap “Next” at top right.
8. Select a site if prompted.
9. Tap “Publish” at top right.
10. View the published post in a browser or preview it in the app.

Result: the markdown for italic, strikethrough, and checkboxes does not work because WordPress.com uses Markdown Extra which appears to be a little different compared to what Bear uses. See https://en.support.wordpress.com/markdown-quick-reference/ and https://en.support.wordpress.com/wordpress-editor/blocks/markdown-block/#markdown-extra-and-markdown-in-jetpack.

^{Tested with WP Internal 12.1.0.20190325 on iPhone 6S iOS 12.2 sharing from Bear into this post on madefortesting190318.wordpress.com.}

Sample content:

# Title
Content.

## Heading 2
*Bold* /italic/ _underlined_ -strikethrough-.

[WordPress](https://wordpress.org/)

- Check!

1. Numbered list item.

* Bulleted list item 1.
* Bulleted list item 2.

[nheagy]

➕1

I'm really hoping we can add Markdown support to our app!

That said, bear's default flavour of markdown (Polar) is odd. We'd probably aim to support their Markdown compatibility mode.

[nheagy]

@designsimply this one may be able to be closed. If sharing from Bear as MD or TextBundle, Markdown should now work. Tho Polar format is still not supported.

[designsimply]

Okay. I will re-test it soon!

[stale[bot]]

This issue has been marked as stale because:

• It has been inactive for the past year.
• It isn't in a project or a milestone.
• It hasn’t been labeled [Pri] Blocker, [Pri] High, or good first issue.

Please comment with an update if you believe this issue is still valid or if it can be closed. This issue will also be reviewed for validity and priority (cc @designsimply).