tpl/tplimpl: Add Mastodon and PeerTube shortcodes

[thilop]

Currently, Hugo supports embedding content from popular platforms like YouTube an X, but there is no built-in support for embedding content from Fediverse services such as Mastodon, Pixelfed, or PeerTube. These platforms are gaining significant traction due to their decentralized nature and privacy-respecting approach.
Feature Request:

Provide a way to easily embed posts, images, or videos from Fediverse platforms, including but not limited to:

• Mastodon: Embed public posts and profiles.
• Pixelfed: Embed public images or galleries.
• PeerTube: Embed videos or channels.

[jmooring]

Mastodon posts and PeerTube videos are pretty straightforward via their public APIs:

git clone --single-branch -b hugo-github-issue-13280 https://github.com/jmooring/hugo-testing hugo-github-issue-13280
cd hugo-github-issue-13280
hugo server

But Pixelfed's API requires an authorization header (i.e., you need to generate a personal access token). That added complexity makes this an unlikely shortcode candidate.