#311 prerelease deployment

[michaelwittwer]

this pull request contains two main features:

• Replace travis build with github-action build

• To be able to release preview functionality via npm we can update the .releaserc.json file to allow a branch to be published, this process is for now not tied to the creation of a PR for a certain branch. This would be the desired behavior, but for now we just allow a more manual approach.

  The channel defines the npm dist-tag and the prerelease defines the v5.8.0-pr311.1 (bold part), those two values should always be equal.

  With this setup consumers are able to install prerelease version using the command npm i @shiftcode/dynamo-easy@pr311

[coveralls]

Coverage remained the same at 95.61% when pulling 72058fa0d337efdbf873ecf31e1c141e4f24ed5a on #311-prerelease-deployment into 3ffded4f059bfb2cf28b7740979d29a6b9b3d371 on master.