feat: parse HTML element and attribute positions

[alehechka]

Overview

This PR adds positions to the templ parser results for HTML elements and attributes relating to conversation in #498, specifically the recommendation made in #498 (comment).

This handles only calculating expression positions. I plan to open another PR when ready to use the calculated positions to enable LSP intellisense with a few hard-coded results. After that, I can work towards the solution I recommended in #498 (comment), to import an HTML LSP's data into templ's LSP.

[alehechka]

@a-h, I finished getting all the unit tests updated to reflect the position calculations so this should be ready for code review now.

[joerdav]

My immediate thoughts here are that maybe Expression isn't the right type, so far I think we only store Go in here.

I could be being nit-picky but I think it makes more sense for there to be an HTML specific expression type.

[alehechka]

@joerdav, that sounds valid. I mainly reused it since it was already a pattern for storing positions. Should be simple enough to do a find and replace with a new name. Do you have anything in mind as an alternative to Expression?

[alehechka]

Considering that Expression.Value ends up with the same value as Name from the parent struct in all of these cases, we could probably just use Range directly to store the positions of elements/attributes.

[alehechka]

@joerdav, I went ahead and replaced Expression with Range in all cases. Let me know if this approach works better with you.

[joerdav]

@alehechka the type range makes sense, happy with that. I wonder if a better name for the property could be in order? The name Range Range to me suggests it's the range of the whole open tag, maybe NameRange Range could be more specific? After that I'm happy with this PR if @a-h is.

[alehechka]

@joerdav @a-h
I updated those fields to NameRange as recommended.