Create rpm package

[srueegger]

This pull request introduces Fedora RPM packaging for the project and updates the version to 1.2.1 across all relevant files. The most significant changes are the addition of automated GitHub Actions workflows for building RPMs for Fedora 43 (both x86_64 and ARM64), the inclusion of a new bootmate.spec file for RPM packaging, and corresponding documentation and metadata updates to reflect the new version and packaging support.

Fedora RPM packaging support:

• Added .github/workflows/build-rpm-fedora.yml and .github/workflows/build-rpm-fedora-arm64.yml workflows to automate RPM builds for Fedora 43 (x86_64 and ARM64) on release and manual dispatch. These workflows handle dependency installation, source tarball creation, RPM building, and artifact upload. [1] [2]
• Added a new bootmate.spec file describing the RPM package, its dependencies, build instructions, and included files.

Version bump and metadata updates:

• Updated the project version to 1.2.1 in Cargo.toml, meson.build, translation files (po/de.po, po/en.po), documentation (RELEASE.md, README.md), and the new bootmate.spec file. [1] [2] [3] [4] [5] [6] [7]
• Updated data/ch.srueegger.bootmate.metainfo.xml.in to add release entries for 1.2.1 and 1.2.0, including mention of RPM builds in the changelog. [1] [2]

Automation improvements:

• Enhanced update-version.sh to automatically update the version in bootmate.spec and include it in the list of files updated during version bumps. [1] [2]