add Go aiscat binding

[ngtrthanh]

Summary

Adds a Go module under go/aiscat that binds AIS-catcher's existing C++ NMEA-to-JSON decoder through cgo. The API mirrors the Python aiscat package with a streaming Decoder, one-shot decode helpers, reader/TCP/UDP stream helpers, and the same output formats: dictionary, annotated, json, json_nmea, nmea, nmea_tag, and binary.

The native bridge compiles the same focused AIS-catcher source subset used by the Python binding (Marine, JSON, Library, and Utilities) and keeps the host-language layer thin.

User Impact

Go users can consume AIS-catcher's decoder directly from Go services without shelling out to the CLI, while retaining output compatibility with AIS-catcher JSON and the Python binding behavior.

Notes

• Requires cgo and a C++11 compiler.
• Includes a no-cgo fallback with a clear runtime error.
• README documents Windows verification with Zig.

Validation

Ran from go/aiscat:

go test ./...
$env:CGO_ENABLED='1'; $env:CC='zig cc'; $env:CXX='zig c++'; go test ./...
$env:CGO_ENABLED='1'; $env:CC='zig cc'; $env:CXX='zig c++'; go run .\examples\decode