ENH Adds ability to create table of contents

[lazarust]

Closes: #302

[BenjaminBossan]

Regarding not needing an extra utility function: you're right, we should keep it simple for now, this is sufficient.

Regarding your implementation, I think it won't work if you plan to use the anchors as they need to be lower-cased and may not contain white spaces (SO). Also not sure if we need links at all, as a user can't do anything with those, except when they're rendered, but as is, the rendered model card won't contain the TOC.

Moreover, four spaces looks excessive to me. I think 2 spaces should be enough to be rendered correctly.

Finally, could you please add some tests?

[lazarust]

@BenjaminBossan This is ready for you to review again!

[BenjaminBossan]

From my point of view, we're pretty close now. Just a few small changes.

Maybe @adrinjalali you could also take a quick look to see if this feature makes sense?

[lazarust]

@BenjaminBossan and @adrinjalali I've addressed all your comments other than including the Table of Contents in the markdown

[lazarust]

@adrinjalali I've addressed your comments! Sorry, it took a while!

[adrinjalali]

Thanks @lazarust

[lazarust]

@adrinjalali and @BenjaminBossan This is ready for y'all to look at again!

[adrinjalali]

Thanks @lazarust , I'll let @BenjaminBossan have the final look.

[BenjaminBossan]

Thanks a lot!