ask.el -> ask-mode.el and add file header

[yuanwang-wf]

Greeting, thank you for putting this project on github, and CS103 2024/25 lectures on the internet.

I think this PR makes install ask mode in emacs easier.

once again, thank you for all the work.

[fredrikNordvallForsberg]

Could you briefly explain why this makes it easier to install ask?

I spoke to @pigworker, and they were reluctant to accept this pull request during the semester, as it would mean having to change the file name in their .emacs file.

[yuanwang-wf]

Could you briefly explain why this makes it easier to install ask?

I can try. I was packaging this with nix using nix's melpa build. I think under the hook, it tries to package all el files (in this case just one file) as a melpa package. The build failed because

1. the file doesn't have a file header ;;; file-name.el --- some comment
2. at the end of file, file (provide 'ask-mode), but the file's name is not ask-mode

I based the change from agda2-mode https://github.com/agda/agda/blob/master/src/data/emacs-mode/agda2-mode.el

We can wait until the semester finish or close this PR. I can keep this PR up to date

[fredrikNordvallForsberg]

Thanks for explaining! I think merging after the semester finishes seems like a good plan, if you are happy with that?

[yuanwang-wf]

that sounds good to me, thank you!