Javascript bindings (#14)

* Initial version ready

- bindings are in `bindings/emscripten.cpp`
- minimal Javascript example is in `examples/ggwave-js`

* add npm package + add test-ggwave.js

* js : rename export name to "ggwave_factory"

* update to v0.1.5

* Update README.md

* npm : add npm-publish target

bindings/javascript/CMakeLists.txt

@@ -0,0 +1,24 @@
+set(TARGET libggwave)
+
+add_executable(${TARGET}
+    emscripten.cpp
+    )
+
+target_link_libraries(${TARGET} PRIVATE
+    ggwave
+    )
+
+set_target_properties(${TARGET} PROPERTIES LINK_FLAGS " \
+    --bind \
+    -s MODULARIZE=1 \
+    -s SINGLE_FILE=1 \
+    -s ALLOW_MEMORY_GROWTH=1 \
+    -s EXPORT_NAME=\"'ggwave_factory'\" \
+    ")
+
+add_custom_command(
+    TARGET libggwave POST_BUILD
+    COMMAND ${CMAKE_COMMAND} -E copy
+    ${CMAKE_BINARY_DIR}/bin/libggwave.js
+    ${CMAKE_CURRENT_SOURCE_DIR}/ggwave.js
+    )