Is there a way to disable updates of specific nuget packages installed in a project?
I have made some local modifications to a couple of javascript library packages
You could try constraining the package so it your project will only allow a particular version to be used. Then all updates to any newer version will be prevented.
You can do this by editing your project's package.config file. For example, the line below should only allow version 2.1.0 to be used.
<package id="SomePackage" version="2.1.0" allowedVersions="[2.1.0]" />