Add node 6, 10 and 14 to GitHub Actions and Azure Pipeline tests

[kuleshovilya]

Add node 6, 10 and 14 to GitHub Actions and Azure Pipeline tests, lower npm requirements in make.js due to it being unable to use node 6

[DaniilShmelev]

Just curious - why do we have both github actions and azure pipelines CI? As I can see, github actions runs npm run build and npm test, and azure pipelines runs npm run units. Should we merge them/get rid of one of them?
I think it would be easiest to just add npm run units command to github actions and remove azure pipelines.
@anatolybolshakov what do you think?

[alexander-smolyakov]

Just curious - why do we have both github actions and azure pipelines CI? As I can see, github actions runs npm run build and npm test, and azure pipelines runs npm run units. Should we merge them/get rid of one of them?
I think it would be easiest to just add npm run units command to github actions and remove azure pipelines.
@anatolybolshakov what do you think?

@DaniilShmelev, the azure pipeline also publishes the build artifact that we could use later to publish the package to npm.

typed-rest-client/azure-pipelines.yml

Lines 38 to 44 in 8bdfb96

	# publish build artifacts to drop folder so we can use them for release
	- task: PublishBuildArtifacts@1
	inputs:
	PathtoPublish: "_build"
	ArtifactName: "drop"
	ArtifactType: "Container"
	displayName: Publish build artifacts

Overall I agree with the idea to merge these pipelines into one and if we will decide to do this let's save the pipeline in Azure.

[kuleshovilya]

@alexander-smolyakov @DaniilShmelev So, what are we deciding on? Merging both tasks, as in adding unit tests and publish build to a github actions and removing azure pipelines, while saving it to azure repo?

[alexander-smolyakov]

@kuleshovilya I would like to suggest the following approach:

1. Merge this PR
2. Update related Azure pipeline and remove GitHub action
3. Open another PR