Update Emscripten build configuration

Removed `.mjs` extension and added TypeScript definition generation for the Emscripten build. This change ensures compatibility with web environments and improves developer experience with TypeScript by generating the `OasisC.d.ts` file.

CMakeLists.txt

@@ -13,8 +13,7 @@ set(OasisC_SOURCES
 
 if (DEFINED EMSCRIPTEN)
  add_executable(OasisC ${OasisC_SOURCES})
- set(CMAKE_EXECUTABLE_SUFFIX ".mjs")
- target_link_options(OasisC PUBLIC -sSINGLE_FILE --no-entry "-sEXPORT_NAME='OasisC'" "-sEXPORTED_RUNTIME_METHODS=ccall,cwrap")
+ target_link_options(OasisC PUBLIC -sSINGLE_FILE --no-entry "-sEXPORT_NAME='OasisC'" "-sEXPORTED_RUNTIME_METHODS=ccall,cwrap" "-sENVIRONMENT='web'" "--emit-tsd OasisC.d.ts")
 else ()
  add_library(OasisC ${OasisC_SOURCES})
 endif ()