changing insertHorizontalRule hotkey description

[tandcode]

Description

The "ctrl+shift+alt+_" hotkey does't work with underscore, but the "ctrl+shift+alt+-" works well.

Checklist:

• [x] I've read and understood the contribution guidelines
• [x] I've tested my changes against at least one of the following Anki builds:
  • [x] Latest standard Anki 2.1 binary build [required for Anki-compatible 2.1 add-ons]
  • [ ] Latest alternative Anki 2.1 binary build
  • [ ] Latest Anki 2.0 binary build [required for Anki 2.0-compatible add-ons]
• [x] I've tested my changes on at least one of the following platforms:
  • [ ] Linux, version:
  • [x] Windows, version:
  • [ ] macOS, version:
• [ ] My changes potentially affect non-desktop platforms, of which I've tested:
  • [ ] AnkiMobile, version:
  • [ ] AnkiDroid, version:
  • [ ] AnkiWeb

[glutanimate]

Hey @tandcode, Thanks for the contribution and my apologies for taking so long to review this.

Hmm, what keyboard layout are you using, if I may ask? I just tested the add-on again, and it seems like both variants (ctrl+shift+alt+_ and ctrl+shift+alt+-) work for me. However, I am using a German keyboard layout, and on there - and _ are bound on the same key, with Shift+<key> yielding _.

My concern with merging this PR is that I don't know what effect this will have on other keyboard layouts, and since is the first report to the effect that the binding is not working, I'm afraid it might break for other users.

[glutanimate]

Coming back to this: I assume that finding shortcuts that work for all layouts will never 100% work, and right now I am not sure which one between the current assignment and the suggested assignment is supported more widely. So for now I'm closing this issue, but will try to re-evaluate the defaults in the future.