Bump libpgfmt to 1.1.2 and version to 2.1.2

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

## What's Changed

### Improved
- Updated internal dependencies: libpgfmt from 1.1.0 to 1.1.1 ([#6](#6))
- Added Homebrew formula update automation to the release workflow

Bump version to 2.1.0

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Bump version to 2.0.0

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

## What's Changed

### Added
- New SQL formatting styles: dbt-modern (lowercase keywords), GitLab, Kickstarter, and mattmc3 modern SQL ([#2](#2))
- AWeber-style formatter with river alignment, CASE expression formatting, and nested CTE support ([#1](#1), [#2](#2))
- River-style SQL formatter as the base for alignment-driven styles, including subquery indentation, CTE support, and CREATE TABLE/VIEW/FUNCTION/DOMAIN/MATERIALIZED VIEW ([#1](#1))
- Mozilla-style SQL formatter ([#1](#1))
- CLI and Python library API with passthrough for unsupported statement types
- MkDocs documentation for CLI, API, and all formatting styles

### Fixed
- Nested CTE river width inheritance: width is now always computed as the maximum of the inherited width and the local unified river width, ensuring consistent alignment across nested WITH scopes ([#2](#2))
- CASE expression multi-line THEN/ELSE value indentation in AWeber style ([#2](#2))
- Integer and float zero literal parsing
- USING clause preservation and passthrough output normalization in Mozilla style
- CREATE FUNCTION STRICT/SECURITY option parsing