Update access-kit to 0.18.0 (#140)

Author: bruvzg

build.sh

@@ -170,7 +170,7 @@ if [ ! -d "deps/accesskit" ]; then
   echo "Missing accesskit, downloading it."
   mkdir -p deps/accesskit
   pushd deps/accesskit
-  curl -L -o accesskit.zip https://github.com/godotengine/godot-accesskit-c-static/releases/download/0.17.0/accesskit-c-0.17.0.zip
+  curl -L -o accesskit.zip https://github.com/godotengine/godot-accesskit-c-static/releases/download/0.18.0/accesskit-c-0.18.0.zip
   unzip -o accesskit.zip && rm -f accesskit.zip
   mv accesskit-c-* accesskit-c
   popd