Add sample support to all templates (except DDP)

[yogan]

Has input.txt, but no sample.txt:

• [x] Clojure
• [x] Elixir
• [x] Kotlin
• [x] Zig

[yogan]

Ideally take this approach: ./run.sh [FILENAME], with a default to input.txt when no argument is given.

Adapt the scripts of all templates to use this pattern (don't forget about READMEs).