[site/links]: add support for next links in markdown

[khalilcodes]

Add support for next links (internal links) in markdown

Resolves #170

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This PR adds support for next links ie, <Link href="..." /> in markdown to handle site's internal links. Also, external links will be open in a new tab. And finally, links that end with .md are replaced with path only.

Tasks:

• [x] Handle hrefs ending with .md
• [x] Add internal links check for heading and tooltips to handle accordingly
• [x] Handle external links to open in new tabs
• [x] Change source file path based on href above in tooltip component

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