build: release v3.4.3

[galtm]

This pull request brings the Oxygen add-on up to date with xspec/xspec#2282.

To do, in this order:

• Merge build: release v3.4.3 xspec#2282 into master. That will create the v3.4.3.zip file.
• On the branch for this PR, run hugo locally and test installation of the add-on with local URL: http://localhost:1313/editors/oxygen/oxygen-addon.xml
• Merge this PR onto hugo branch.
• Uninstall add-on, and test re-installation with remote URL: https://xspec.io/editors/oxygen/oxygen-addon.xml

Cc: @cmarchand