add brotli.jam

[ashtum]

Proposed changes

Add brotli library support to B2 build system. This introduces a new brotli.jam tool module that provides configuration and detection for the brotli compression library. After using brotli, the following targets become available:

• /brotli//brotlicommon -- The brotli common library
• /brotli//brotlidec -- The brotli decoder library
• /brotli//brotlienc -- The brotli encoder library

Types of changes

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• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Documentation content changes
• Other (please describe):

Checklist

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• I searched the discussions
• I searched the closed and open issues
• I read the contribution guidelines
• I added myself to the copyright attributions for significant changes
• I checked that tests pass locally with my changes
• I added tests that prove my fix is effective or that my feature works
• I added necessary documentation (if appropriate)

Further comments