Proper Release Management

[maybeec]

Currently we have old and way too much devonfw_guide.pdf files in the history.

• Please cleanup the history and remove the pdf file from history entirely. The repository is much too big already slowing down all our github action builds.
• The hint in the readme needs to be deleted as well. The repository already reached 2GB of space just on the main branch which slows down so many clones and github actions like the website without any necessity.

Instead I would suggest the following:

• whenever there is a git tag created and successfully built on one of the assets integrated as submodule in this repository, the devonfw-guide pdf should deployed as a GitHub release with the following tag and release name: $TAG_YEAR.$TAG_MONTH.$GITHUB_RUN_NUMBER whereas TAG_YEAR and TAG_MONTH has to be derived from the new tag of the submodule triggering the build (possibly passed as a parameter or discovered from the history). Be aware that currently we have different tag schemes like 2021.04.001 or v2021.04.001 or even release/2021.04.001 all should be valid, and you should identify the sequence 2021.04 automatically in all cases and append .$GTHUB_RUN_NUMBER to it.
• Please attach / upload the devonfw_guide_$TAG_YEAR.$TAG_MONTH.$GITHUB_RUN_NUMBER.pdf to the github release.