Add HTTP proxy functionality

Signed-off-by: Florian Hopfensperger <florian.hopfensperger@allianz.de>

- lower proxy functionality to Https for now (the general proxy package adds a ton of dependencies - which are difficult to review)

Add octokit documentation

Signed-off-by: Florian Hopfensperger <florian.hopfensperger@allianz.de>

Lint & build & packaged

Signed-off-by: Florian Hopfensperger <florian.hopfensperger@allianz.de>

README.md

@@ -178,6 +178,8 @@ jobs:
 
 > **Note**: By default not specifying `fromTag` or `toTag` will resolve `toTag` from either the `ref` or alternatively fallback to the latest tag from the git API. `fromTag` is resolved by sorting tags using [semver](https://semver.org/). Check the [configuration](#configuration-specification) for alternatives.
 
+> **Note**: If you are behind a corporate HTTP proxy, you can set the `https_proxy` environment variable to the proxy URL. For reference, please see the Octokit [documentation](https://github.com/octokit/octokit.js/#proxy-servers-nodejs-only).
+
 ### Configuration
 
 The action supports flexible configuration options to modify vast areas of its behavior. To do so, provide the configuration file to the workflow using the `configuration` setting.