Your Project Title

As a test, I rewrote the GitHub Flavored Markdown Admonitions plugin as a Converter: jekyll-gfm-admonitions.rb.

Gemfile:

group :jekyll_plugins do
  gem 'jekyll-gfm-admonitions', git: 'https://github.com/manabu-nakamura/jekyll-gfm-admonitions2'
end

_config.yml:

plugins:
  - jekyll-gfm-admonitions

.md:

> [!NOTE]
> foo
> bar
  baz
qux

quux

⬇️Markdown processor?

<blockquote>
<p>[!NOTE]
foo
bar
baz
qux</p>
</blockquote>
<p>quux</p>

⬇️GFMAdmonitionConverter

<div class='markdown-alert markdown-alert-note'><p class='markdown-alert-title'><svg class="octicon octicon-info" viewBox="0 0 16 16" version="1.1" width="16" height="16" aria-hidden="true"><path d="..."></path></svg> Note</p>foo
bar
baz
qux</div>
<p>quux</p>

⬇️

Note

foo bar baz qux

quux

https://manabu-nakamura.github.io/jekyll-gfm-admonitions2/, https://manabu-nakamura.github.io/jekyll-gfm-admonitions2/README2.html, https://github.com/manabu-nakamura/jekyll-gfm-admonitions2

> foo
> bar
  baz
qux

quux
> [!NOTE]
> foo
> bar
  baz
qux

quux
> foo
> bar
# H1
> [!NOTE]
> foo
> bar
# H1
> [!NOTE] My own title
> Fancy!

  > [!NOTE] My own title
  > Fancy!

    > [!NOTE] My own title
    > Fancy!

> [!NOTE] My own title
> > [!NOTE]
> > foo

> [!NOTE]
> > [!NOTE]
> > foo

> [!NOTE]
> foo
> > [!NOTE]
> > bar

> foo
> > [!NOTE]
> > bar

⬇️

foo bar baz qux

quux

Note

foo bar baz qux

quux

foo bar

H1

Note

foo bar

H1

My own title

Fancy!

My own title

Fancy!

> [!NOTE] My own title
> Fancy!

My own title

[!NOTE] foo

Note

[!NOTE] foo

Note

foo

[!NOTE] bar

foo

Note

bar

Manabu Nakamura