Declare peer dependency on html-webpack-plugin

[jscheid]

Closes #90

[clydin]

This should be reverted. Causing a peer dependency warning when the html-wepback-plugin is not in use is an error. Peer dependencies are require dependencies and html-wepback-plugin is not required for this plugin to function (the code is designed to specifically account for that fact). There are legitimate use cases where not using the HTML plugin is completely acceptable. Once of which this the Angular CLI, which cannot currently update the version of this plugin due to this PR's change.

[jscheid]

@clydin could I ask you to comment on #90 instead?

[clydin]

It’s closed and this PR is the underlying issue. Unfortunately, If this is not addressed we’ll be forced to consider creating an alternative plugin to handle SRI.

[jscheid]

I think it would be good if we could continue the conversation on #90, especially because the original impetus for the change request appears to be angular/angular-cli#12465 and you seem to be in a good position to comment on that.

Feel free to reopen the issue.

FWIW, I'm generally not opposed to the idea of reverting a change that does more harm than good.