[docs] Added version switcher.

Preview is here: https://ogs.ogs.xyz/-/tools/ogstools/-/jobs/376612/artifacts/public/index.html

Please note the shown version (0.2.0) in the switcher is just for testing and will be removed later on.

• Migrate ogs.org domain from Azure
• Setup custom domain ogstools.opengeosys.org on https://gitlab.opengeosys.org/ogs/tools/ogstools-docs
• Set URLs
• Merge
• Create a release
• Upload release manually to ogstools-docs-repo