feat: add reactions to question & answer

[hgaol]

close #883 .

done backend:

• used meta table to save reactions.
• created 2 APIs. one is to retrieve meta for an object, the other is to add or update.

frontend:

• added an Reaction component.
• to make it easy to determine if it's need to show the Add a comment button, place it in the Comment component.

todo

• [x] add i18n for reactions.

[hgaol]

some screenshots.

[hgaol]

add i18n.

[LinkinStars]

@hgaol It's great, and the backend tasks were almost done. It's ready for the frontend to review. @shuashuai

[hgaol]

Really appreciate @LinkinStars and @shuashuai for your careful and patient review! thanks!

[PrimmaAnna]

@hgaol Hey, I sent you an email like a week ago, but haven't got your replied yet. Could you please check on your email box please? Thanks 😀

[hgaol]

@hgaol Hey, I sent you an email like a week ago, but haven't got your replied yet. Could you please check on your email box please? Thanks 😀

Hi @PrimmaAnna , thanks for reaching out! Sorry that I haven't monitored my email account recently. Just replied that email. Thanks!