Swift: update README.md with IDE setup

Author: redsun82

swift/README.md

@@ -33,3 +33,20 @@ bazel run //swift/codegen
 
 to update generated files. This can be shortened to
 `bazel run codegen` if you are in the `swift` directory.
+
+## IDE setup
+
+### CLion and the native bazel plugin
+
+You can use [CLion][1] with the official [IntelliJ Bazel plugin][2], creating the project from scratch with default
+options. This is known to have issues on non-Linux platforms.
+
+[1]: https://www.jetbrains.com/clion/
+
+[2]: https://ij.bazel.build/
+
+### CMake project
+
+The `CMakeLists.txt` file allows to load the Swift extractor as a CMake project, which allows integration into a wider
+variety of IDEs. Building with CMake also creates a `compile_commands.json` compilation database that can be picked up
+by even more IDEs. In particular, opening the `swift` directory in VSCode should work.