Signature-Pad is not working in Launchpad

HI Experts,

I have a requirement for digital signature pad in SAP UI5 Application and it is working fine running application with index.html, where I am adding script of Signature-pad in index.html file, whereas it is throwing error 'SignaturePad is not defined' in Fiori Launchpad. How can I add Signature-Pad library in launchpad? Below is the error I am facing in launchpad :-

Thing I have tried:-

1. Installing the library inside my project using npm install --save signature_pad (no luck).

2. Downloading library and calling inside controller (no luck).

3. Adding library in manifest.json file i.e "js": [ {"uri": "/your/lib/name.js" } ] (no luck).

Can someone please help, why after adding and installing the signature library it is not working in launchpad?

Thanks in advance..!!