Support non-bundler package managers

[MPV]

Instead of hardcoding/requiring bundler, allow the upstream detection, as per:

By default, license_finder will check for all supported package managers
-- https://github.com/pivotal/LicenseFinder#narrow-down-package-manager

[ralexander-phi]

Thanks for the PR!

Is there a specific language or package manager you're looking to support? I'd like to add a test and update the README.

Looking at this with fresh eyes I'm wondering why I'm doing the bundle install in the action instead of requiring that the user perform the install themselves in an earlier workflow step.

[MPV]

Is there a specific language or package manager you're looking to support? I'd like to add a test and update the README.

I'm mainly looking for:

• NPM
• SBT
• Maven

[MPV]

Looking at this with fresh eyes I'm wondering why I'm doing the bundle install in the action instead of requiring that the user perform the install themselves in an earlier workflow step.

Yeah I wondered that too.
Shall we remove it?
Makes sense to me too.
Either that, or doing the equivalent for all package managers. But I'm not sure which way would work best together with the upstream tool, input/experience welcome.

[ralexander-phi]

I tried out a couple things, but I don't think this will work as-is. The current action uses the ruby Docker image, which doesn't have npm or other package managers installed. So license_finder fails to find npm (and other tools) even though previous steps may have used them. I think I chose wrong with the Docker image approach.

I got this working with a composite action instead. The composite action runs in the same container previous steps used, so it finds npm (and other tools) that earlier steps used.

@MPV , can you take a look at #15 and an NPM example. I'd like to add maven and sbt examples for completeness, although I don't usually work with these tools.

[ralexander-phi]

I ran some testing via the testing repo, I think this is good to go. Let me know if you run into any issues.