Add comprehensive TurfJS missing functions analysis

[danfma]

Add comprehensive TurfJS missing functions analysis

Summary

Adds MISSING_FUNCTIONS.md - a comprehensive documentation file that analyzes the gap between TurfJS (114 packages) and the current DotTerritory implementation (72 functions implemented, 45 missing). The analysis was created by comparing the TurfJS repository packages directory with the existing Territory.*.cs files in the DotTerritory codebase.

The file organizes the 45 missing functions into 10 logical categories (Measurement, Feature Conversion, Grids, Classification, etc.) and provides implementation priority recommendations to guide future development work.

Review & Testing Checklist for Human

Since this is documentation-only, the main things to verify are:

• Accuracy of function counts: Spot-check that the "72 implemented" and "45 missing" counts are reasonable by comparing a few examples from the lists against the actual codebase
• Priority recommendations make sense: Review the High/Medium/Lower priority categorizations to ensure they align with the project's goals and typical geospatial use cases

Notes

• This is a documentation-only change with no code modifications
• The analysis provides a roadmap for future TurfJS porting work with checkbox tracking
• Some functions may be intentionally excluded if they conflict with NetTopologySuite's approach
• Link to Devin run: https://app.devin.ai/sessions/76709c83b842485a95ce90ef3903c563
• Requested by: Daniel Ferreira Monteiro Alves (@danfma)

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[Copilot]

Pull Request Overview

This PR adds comprehensive documentation analyzing the gap between TurfJS and DotTerritory implementations by creating MISSING_FUNCTIONS.md. The analysis reveals that 72 out of 114 TurfJS functions are implemented (63%), with 45 functions remaining to be ported.

• Creates structured documentation categorizing 45 missing TurfJS functions into 10 logical groups
• Provides implementation priority recommendations (High/Medium/Lower) to guide future development
• Documents all 72 currently implemented functions for reference

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