Change the default downloaded file name to "filename_signed_by_OpenSign™.pdf"

[nxglabs]

Change the default filename generated when a signed document is downloaded from "filename_signed_by_opensign.qik.ai.pdf" to filename_signed_by_OpenSign™.pdf"

[nxglabs]

@all-contributors please add @Tashuuuu for code

[allcontributors]

@nxglabs

I've put up a pull request to add @Tashuuuu! 🎉