Add tile encoder to complement existing decoder

[Copilot]

Implementing minimal tile encoder functionality to complement the existing decoder:

• Understand current decoding flow (VectorTileParser → VectorTileLayer → VectorTileFeature)
• Create VectorTileEncoder class with Encode method (reverse of Parse)
• Create GeometryEncoder class (reverse of GeometryParser)
• Create AttributesEncoder class (reverse of AttributesParser)
• Add encoder tests to validate round-trip encoding/decoding (5 tests total)
• Update documentation with encoder usage examples
• Run all tests to ensure no regressions (28/28 tests pass, 1 network test expected to fail)
• Request code review (fixed issue with ClosePath command)
• Run security checks (no vulnerabilities found)
• Make VectorTileEncoder.Encode return Stream for fluent API

Summary

This PR adds a complete tile encoder to the library, enabling users to create Mapbox vector tiles programmatically. The encoder:

• Supports all geometry types (Point, LineString, Polygon)
• Properly encodes attributes with type preservation
• Uses ZigZag encoding for coordinates
• Follows the Mapbox Vector Tile specification
• Has been validated with round-trip tests on real tiles
• Returns the stream for method chaining and fluent API usage

All 28 tests pass successfully.

Original prompt

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This section details on the original issue you should resolve

<issue_title>add tile encoder</issue_title>
<issue_description></issue_description>

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

@bertt no work has not started on this, better use one of the tools at https://github.com/mapbox/awesome-vector-tiles for encoding tiles @bertt Some discussion on https://github.com//issues/9

• Fixes add tile encoder #1

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[bertt]

@copilot make vector tile encoder return the stream

[Copilot]

@copilot make vector tile encoder return the stream

Done. Changed VectorTileEncoder.Encode() to return the stream instead of void. This allows for fluent API usage. (f3b725f)

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