Implement canvas zoom legacy keyboard shortcuts

[Keyikedalube]

Maintainers, it's possible to have two keyboard shortcuts at the same time. For now, we have this PR implementing Inkscape style shortcuts

1. canvas-zoom-in   : =
2. canvas-zoom-out : -
3. canvas-zoom-fit   : 0

The above new canvas zoom shortcuts is already paving way for UX consistency for issue #1122

However, if you want to keep the legacy style

1. canvas-zoom-in   : Ctrl + =
2. canvas-zoom-out : Ctrl + -
3. canvas-zoom-fit   : Ctrl + 0 <--- New

It's possible with this PR #1776 I made; hidden menubar

So it's a win-win for both parties; improved vs legacy

Originally posted by @Keyikedalube in #1769 (comment)

[Keyikedalube]

👉 Easy and good first issue 👈

[Keyikedalube]

I guess it's OK now to remove the Hacktoberfest label.

[DhairyaBahl]

@Keyikedalube @ice0 I would like to work on this issue. It is much more like the previous issue that I solved of keyboard shortcuts.
Kindly Assign it to me. :)

[Keyikedalube]

:) Thanks for wanting to tackle this issue!

Go make that PR

[DhairyaBahl]

@Keyikedalube I wanted to know,

• Do I have to add legacy key controls as normal method?? Will They Work ??
• Or do i have to use hidden menubar you created ??

Kindly tell me. Thanks :)

[Keyikedalube]

hidden menubar

[Keyikedalube]

Linked PR merged. Issue fixed.