Add Zeckendorf in Algol68

[rzuckerm]

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I Am Adding a New Code Snippet in an Existing Language

• I fixed Add Zeckendorf in Algol68 #5303
• I did not include any extra folders/libraries
• I named the pull request using Add {PROJECT} in {LANGUAGE} format

[jrg94]

The keyword "on" looks so odd. I love it.