experimental Extism cpp-pdk ideas

#define EXTISM_IMPLEMENTATION
#include "extism-pdk.hpp"

static constexpr const auto Greeting = "Hello";

int32_t EXTISM_EXPORTED_FUNCTION(greet) {
  std::string input = self.input<std::string>();
  std::string config = self.config("user");
  std::string var = self.var.get("var");
  self.console.warn("input=%s config.user=%s var.var=%s // var.var=%s\n", input.c_str(), config.c_str(), var.c_str());
  self.formatOutput("%s, %s", Greeting, input.c_str());
  return 0; 
}

extism call plugin.wasm greet --input="tim"
# => Hello, tim

• see plugin.cpp for a few additional examples
• make fetch-linux-sdks to summon dependencies on linux
• make test to compile across emscripten, wasi-sdk, and system clang++