Improved keyboard accessibility of the find-replace popup

[SundeepChand]

Fixes #1699
I have verified that this pull request:

• has no linting errors (npm run lint)
• is from a uniquely-named feature branch and has been rebased on top of the latest develop branch. (If I was asked to make more changes, I have made sure to rebase onto develop then too)
• is descriptively named and links to an issue number, i.e. Fixes #123

Hello @catarak. Please review my work and please verify the Spanish & Japanese translations of 'Toggle Replace'.

[catarak]

@koji can you verify the Japanese translation?

@oruburos can you verify the Spanish translation?

Thank you!!

[oruburos]

@catarak All good in the Spanish translation.

[koji]

@catarak I would recommend this, 置換の切り替え instead of the current トグル置換.
@SundeepChand, could you change this ↑, please?

By the way, thank you for the release, one person told me that the translation has been released.
https://twitter.com/takawo/status/1329613670188367872

[SundeepChand]

Hello @koji, Thanks for your suggestions. I've updated the same.

[catarak]

Thanks for adding those changes @SundeepChand! I was testing the JS changes that you made, and I noticed that now when I click on the "Replace" button, the replace doesn't happen, but it does work when I click "Replace All".

[SundeepChand]

Thanks @catarak for pointing this out, this bug is there in production as well. Its fixed now.