fix: bing webmaster improvements

[therobrob]

• added data-decorative="true" to images, bc it should prevent bing to produce an error
• added missing meta descriptions
• lengthen the meta descriptions of the operator to 140 – 160 characters (contains the most important topics of the content)

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[github-actions]

Hi there! 👋

Thank you for your contribution to the FIP Guide! 🚀
We appreciate your effort in making rail staff travel information more accessible. 🚄

Checklist before merging:

• Added a description to the Pull Request
• Checked the License of new pictures (non-commercial use without attribution)
• Modified content in English
• Modified content in German
• Modified content in French

[MoritzWeber0]

Looks good, but I see some potential to automate the generation of descriptions. I'll work on it and open it as additional PR.