ci: Bump OTP every two months

Every two months, a scheduler will [align the OTP matrix with Debian]( https://packages.debian.org/search?keywords=erlang). [An example of a run](https://github.com/ariel-anieli/erlware_commons/actions/runs/15422659512/job/43401634702). For that, `bump-otp-matrix.py` is introduced. When new versions are available, the GitHub workflow will be updated; therefore a token with workflow permissions is needed. GH issue: #179