feat: simplify ABNF for v0.1 and introduce section in main document

[DecimalTurn]

This PR:

• Simplifies the ABNF diagram
  • No longer include mentions of LS (Line Seperator) and PS (Paragraph Seperator)
• Makes sure the ABNF is self-contained (no longer need to refer to core rules from RFC 5234.
• Makes the railroad diagram more similar with the style of ECMA railroad diagrams
• Makes the railroad diagram easier to read by re-ordering elements to make them closer to where they are needed and put the ones that are obvious at the end to save space in the core of the page.

[Copilot]

Pull request overview

This PR updates the JSONC specification site to better surface and simplify the formal grammar, and refreshes the generated railroad diagram to match the revised ABNF and styling goals.

Changes:

• Add a “Formal grammar” section to the main document linking to the ABNF file and railroad diagram.
• Simplify and make the ABNF more self-contained (removing reliance on RFC 5234 core rules and removing LS/PS mentions).
• Update the railroad diagram generator script and the generated HTML/CSS output to reflect the new grammar and a revised visual style/order.

Reviewed changes

Copilot reviewed 6 out of 7 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
index.markdown	Adds a dedicated section linking to the ABNF grammar and railroad diagram.
grammar/README.md	Updates documented paths/examples to use grammar/JSONC.abnf.
grammar/JSONC.abnf	Simplifies comment terminators and inlines core-rule equivalents (digit/hexdigit), reorders value, and updates string escape hexdigits rule.
generate-railroad.js	Updates default input, adds inlining/reordering logic, and post-processes generated HTML header.
grammar/railroad-diagram.html	Regenerated diagram output reflecting the updated grammar and ordering.
grammar/railroad-diagram.css	Adjusts diagram styling (terminal/nonterminal appearance and labels).

Comments suppressed due to low confidence (1)

grammar/JSONC.abnf:26

• single-line-comment-end allows a bare CR (%x0D), but the spec defines a “line ending” as LF or CRLF (index.markdown:23) and defines single-line comments as continuing until a line ending. Please either (a) remove the standalone CR alternative here so the formal grammar matches the spec’s terminology, or (b) update the spec’s line-ending definition to explicitly include lone CR as well.

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[DecimalTurn]

The suppressed comment:

single-line-comment-end allows a bare CR (%x0D), but the spec defines a “line ending” as LF or CRLF (index.markdown:23) and defines single-line comments as continuing until a line ending. Please either (a) remove the standalone CR alternative here so the formal grammar matches the spec’s terminology, or (b) update the spec’s line-ending definition to explicitly include lone CR as well.

Is actually relevant, the ABNF indeed allows a lone CR as a line-comment-terminator. Similarly, jsonc-parser and EcmaScript also consider that a lone CR is a valid line-comment-terminator. In the case of EcmaScript, a lone CR is a valid LineTerminatorSequence. For these reasons, the text of the spec should actually reflect that acceptance and specify that a lone CR is a valid line line ending.