feat: fix missing createWritable in safari#62

Safari do have a OPFS but it's lacking any good method of writing things to it unless you are not using the `syncAccessHandle` that's only available in web workers. This will patch/repair/polyfill the missing features in the broken api. - `FileSystemWritableFileStream` is added to global scope only if it dose not exist but a File system dose. - `FileSystemFileHandle.prototype.createWritable` is conditionally polyfilled if needed. - note that this will also patch `getFileHandle` to keep track of what the parent directory is as `createWritable` needs to know the path of where it's located in order to re-create the `FileSystemFile` handle inside of a worker ( cuz they can't be structural cloned / postMessaged ) - Safari did also lacked some assertion test to see if the file/folder still existed before doing some kind of operation on them. so some methods have been patched to ensure that they do still exist