Add Conan 2 package support

[RobbieG15]

Motivation

• Provide a Conan 2 recipe and CMake packaging so the library can be consumed as a Conan package and by CMake consumers via an exported nmea::nmea target.
• Modernize the build to install headers, targets, config/version files, and license metadata so downstream packaging and integration are straightforward.
• Ensure public headers include fixed-width integer headers so installed consumers do not get compilation errors.

Description

• Add conanfile.py that uses cmake_layout(), supports shared/fPIC options, builds with CMake, runs cmake.install(), and exposes cmake_file_name/cmake_target_name (exports nmea::nmea).
• Modernize CMakeLists.txt to a newer CMake policy: create an aliased target nmea::nmea, set cxx_std_11, add installation rules for library, headers, license, and export nmeaTargets.cmake plus generated nmeaConfig.cmake/nmeaConfigVersion.cmake.
• Add cmake/nmeaConfig.cmake.in to include the exported targets when installed.
• Add a Conan-style test_package (with test_package/conanfile.py, test_package/CMakeLists.txt, and test_package/src/test_package.cpp) that links nmea::nmea and validates/parses a sample GGA sentence.
• Add explicit #include <stdint.h> to public headers that expose uint8_t/uint16_t types so consumers compiling installed headers have the required definitions.

Testing

• python3 -m py_compile conanfile.py test_package/conanfile.py succeeded to validate the Conan recipe syntax.
• Full CMake build/install and consumer test sequence cmake -S . -B build -DCMAKE_BUILD_TYPE=Release && cmake --build build && cmake --install build --prefix /tmp/nmea-install && cmake -S test_package -B build-test -DCMAKE_PREFIX_PATH=/tmp/nmea-install && cmake --build build-test && ./build-test/test_package succeeded and printed the expected test output.
• Shared-library build cmake -S . -B build-shared -DCMAKE_BUILD_TYPE=Release -DBUILD_SHARED_LIBS=ON && cmake --build build-shared succeeded.
• conan --version could not be run because Conan is not installed in the environment, and attempting python3 -m pip install --user 'conan>=2,<3' failed due to the environment network proxy (403 Forbidden).

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Codex Task