Custom alert markers (for Obsidian Callout style alert)

[tuurep]

Issue: #141

• Enable markers: '*'
• Make svg icon configurable
  • the plugin allows setting the icons in the initialization like

    mdit.use(githubAlerts, {
      ...
      icons: {
        custom1: svgTag1,
        custom2: svgTag2,
        ...
      } 
      ...
    });

  • Make a new option for vivify's config.json, where you can set either octicon by name or svg by path
  • Allow overriding the default GH icons in the same option
• Color configuration
  • To be decided... Setting it via custom stylesheets always works but is it too annoying to configure a marker in 2 separate places?

Limitation of plugin:

Using a custom marker with spaces doesn't work, such as:

> [!Pay Attention]
> Hey

@Tweekism tested that on Obsidian this does work (thanks!), and I think it makes a lot of sense so I'd wish it worked here too.

This however works of course:

> [!custom] Pay Attention
> Hey

Feels like more work though.

Consider sending PR to the plugin if it's easy to add.

[tuurep]

Check if it actually is "Title Case",
However since multi-word markers don't currently work in the plugin, it's not super relevant at the moment

[tuurep]

Confirmed that in Obsidian it's like this:

> [!hello world]

gives Hello world so first letter capitalized only