Add BNF support package documentation

[Copilot]

Adds documentation for the BNF support packages (apyds-bnf/atsds-bnf) which provide bidirectional conversion between DS's S-expression syntax and human-readable infix notation.

Changes

• New section: Support Packages in docs navigation for extensibility
• New file: docs/support-packages/bnf.md with:
  • Installation for Python and JavaScript/TypeScript
  • Parse/unparse usage examples
  • Syntax comparison table (Ds ↔ Dsp)
• Updated: mkdocs.yml navigation structure

Example Usage

from apyds_bnf import parse, unparse

# Dsp → Ds
parse("a, b -> c")
# a
# b
# ----
# c

# Ds → Dsp  
unparse("a\nb\n----\nc")
# a, b -> c

Original prompt

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This section details on the original issue you should resolve

<issue_title>需要在 docs/ 添加对support packages bnf 的介绍</issue_title>
<issue_description>添加一页就行(包括安装和使用), 毕竟挺简单的, 但是应该需要分一个section, 以后有新的support pacakge 也放进去.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes 需要在 docs/ 添加对support packages bnf 的介绍 #96

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[Copilot]

Pull request overview

This PR adds comprehensive documentation for the BNF support packages that provide bidirectional conversion between DS's S-expression syntax (Ds) and human-readable infix notation (Dsp). The documentation is placed in a new "Support Packages" section, establishing a structure for future extensibility as mentioned in the original issue.

Key Changes

• Created a new "Support Packages" section in the documentation navigation to house support library documentation
• Added detailed BNF package documentation including installation instructions for both Python and JavaScript/TypeScript
• Provided usage examples and a comprehensive syntax comparison table showing the conversion between Ds and Dsp formats

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
mkdocs.yml	Added "Support Packages" section to navigation with BNF sub-entry
docs/support-packages/bnf.md	New documentation file covering installation, usage examples, syntax formats, and package information for apyds-bnf and atsds-bnf

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[Copilot]

The documentation for unary operators is inconsistent. The description states unary operators are (~ a) (parenthesized), but the syntax comparison table on line 116 shows ~ a -> b without parentheses. According to the test files, when parsing (Dsp → Ds), unary operators don't require parentheses (~ a -> b), but when unparsing (Ds → Dsp), the output includes parentheses ((~ a) -> b). Consider clarifying this by noting that parentheses are optional for input but included in output, or showing both forms in the table.