feat: add plugin system for processing instructions

[Tygo-van-den-Hurk]

What do you want to request?

Since the registry is already its own thing it would be easy to reuse to make another registry for the processing instructions.

Note

This change would probably requires reworking the parsing logic, but I was already planning on doing that anyways.

Examples of New Instructions

We could add different types of processing instructions as well:

Processing instructions that dynamically add text:

Hello, my username is: <?eval process.env.USER ?? process.env.USERNAME ?>

Importing files

<?include "path/to/some/other/file.xml" ?>

Modifying parsing state

<?markup "Plain" ?>
<?path "custom-prefix:" ?>

Backwards Compatibility

it would not be a breaking change. You could add a Slyde processing instruction that takes in attribute pairs, and then you would have full backwards compatibility.

<?slyde markup="plain" engine="1.0.0" ?>

I assert this issue is relevant

• I assert that I have read the Code of Conduct and agree to abide by it.

• I assert that this is not a duplicate of an existing issue.

Is this issue important to you?

Add a 👍 reaction to issues you find important.