Accept whitespace around = in HTML attributes

[clauderic]

What are you adding in this PR?

@shopify/liquid-html-parser now accepts whitespace around = in HTML attributes, as browsers and the old ohm grammar do.

Before, the recursive-descent parser ended the attribute name at the space and found no =. It then turned each part of the value into an attribute of its own:

Source	Before	After
<img data-ratio = '{{ r }}'>	data-ratio (empty), {{ r }}	data-ratio='{{ r }}'
<img srcset= "{{ a }}, {{ b }} 2x">	srcset= (empty), {{ a }}, ,, {{ b }}, 2x	srcset="{{ a }}, {{ b }} 2x"

Dawn 5's footer has the srcset= "…" form, so this shows up in real themes.

Changes:

• Tokenizer: inside a tag, each whitespace run is now its own Text token.
• Parser: skips those tokens between attributes, before =, and before the value. This matches the old grammar's syntactic attribute rules (AttrDoubleQuoted = attrName "=" doubleQuote …), which skipped space implicitly. Both attribute loops (element and Liquid-branch) share a new parseAttributeAfterName, so curly-quoted values inside an {% if %} in attribute position now get the same double/single mapping as top-level ones. The parser no longer modifies token.start.
• scanForHtmlCloseTag: compares every Text token between </ and >, not just the first one. Without this, the new tokenization would make </script marker> (with a non-breaking space) inside a <script> or <style> body close the tag early and throw. That text is body text, both before this PR and in browsers.

What's next? Any followup issues?

These cases still differ from the HTML tokenizer. None of them changed in this PR:

• a quote inside an attribute name or unquoted value (title=Don't)
• a==b and a=b=c should give the values =b and b=c
• a/b should split into a and b

Tophatting

• New specs in html.test.ts: whitespace on either side of =, newlines around =, unquoted values, attributes inside a Liquid branch, and NBSP close-tag candidates in script and style. Each fails without its fix.
• tokenizer.test.ts updated for the split whitespace tokens.
• liquid-html-parser, prettier-plugin-liquid, theme-check-common and theme-language-server-common pass locally (7,152 tests).
• Prettier now prints data-ratio = 'x' as data-ratio='x'. It used to break the attribute apart.

Before you deploy

• I included a patch bump changeset

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