#132 Write C++ port README.md

Signed-off-by: vityaman <[email protected]>

ports/cpp/README.md

@@ -1 +1,59 @@
 # ANTLRv4 C3 C++ Port
+
+## About
+
+This is a port of the `antlr4-c3` library to `C++`.
+
+Please see the parent [README.md](../../readme.md) for an explanation of the library and for examples.
+
+## Port features
+
+1. Only `CodeCompletionCore` was ported.
+
+2. Supports cancellation for `collectCandidates` method via timeout or flag.
+
+## Requirements
+
+- [C++ 23 standard](https://en.cppreference.com/w/cpp/23) to compile sources.
+
+- [ANTLRv4 C++ Runtime](https://github.com/antlr/antlr4/tree/4.13.1/runtime/Cpp) to compile sources.
+
+- [CMake 3.7](https://cmake.org/cmake/help/latest/release/3.7.html) to build project.
+
+- [ANTLRv4 Tool](https://www.antlr.org/download.html) to build tests.
+
+- [Google Test](https://github.com/google/googletest) to build tests.
+
+## Usage
+
+Currently, there are no other ways to adding C++ port as a dependency other than by copying and pasting the [directory with project's source code](./source/antlr4-c3) into your own project.
+
+## Build & Run
+
+Actual build steps are available at [CMake GitHub Workflow](../../.github/workflows/cmake.yml). 
+
+`ANTLRv4` Runtime and Tool as well as other dependecnies will be downloaded during `CMake` configiration stage.
+
+```bash
+# Clone antlr4-c3 repository and enter C++ port directory
+git clone [email protected]:mike-lischke/antlr4-c3.git
+cd antlr4-c3/ports/cpp # Also a workspace directory for VSCode
+
+# Create and enter the build directory
+mkdir build && cd build
+
+# Configure CMake build
+# - ANTLR4C3_DEVELOPER should be enabled if you are going to run tests
+# - CMAKE_BUILD_TYPE Asan and Tsan are supported too
+cmake -DANTLR4C3_DEVELOPER=ON -DCMAKE_BUILD_TYPE=Release ..
+
+# Build everything
+make
+
+# Running tests being at build directory
+(make && cd test && ctest)
+```
+
+## Contributing
+
+We recommend using [VSCode](https://code.visualstudio.com/) with [clangd extension](https://marketplace.visualstudio.com/items?itemName=llvm-vs-code-extensions.vscode-clangd) as an IDE. There are some configuration files for launching tests in debug mode, `clangd` configuration and more.