[Request][vim9script/en] add vim9script as translation of @hiphish 's legacy vimscript file

[Konfekt]

• I solemnly swear that this is all original content of which @HiPhish is the original author and I just cobbled something together to get it out
• Pull request title is prepended with [language/lang-code] (example [python/fr] or [java/en])
• Pull request touches only one file (or a set of logically related files with similar changes made)
• Content changes are aimed at intermediate to experienced programmers (this is a poor format for explaining fundamental programming concepts)
• [] If you've changed any part of the YAML Frontmatter, make sure it is formatted according to CONTRIBUTING.md which does not exist, so rather yes?
  • [] Yes, I have double-checked quotes and field names! Which field names?