feat: add displayImageAsHtml and removeOutgoingLinkBrackets options

[bruce3x]

I've added two options to improve the experience of exporting markdown.

1. displayImageAsHtml

When this option is enabled, the tag replaces the traditional markdown image usage. The tag controls the size of the image displayed in markdown preview, in keeping with the experience in obsidian.

In obsidian:

![[image.png|400x300]]

In markdown:

<img src="attachment/image.png" style="width: 400px; height: 300px;" />

2. removeOutgoingBrackets

When this option is enabled, the square brackets around the outgoing links are removed for a better look.

In obsidian:

Here is the [[another-note]].

In markdown:

Here is the another-note.