perf(ui): Improve dark theme

[mofazhe]

The modifications are as follows:

1. menu supports dark
2. dialog supports dark
3. menu icon of EnvironmentModal supports dark
4. alert confirm prompt supports dark
5. tip text of SidebarSettingsModal supports dark

The preview is as follows:

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[flawiddsouza]

Looks good.

Can we retain the original look of the prompt modal for the focus, button colors + button text at least for the light mode?

Before:

After:

It used to look good. The current version looks fine for the dark mode but looks a bit dull for the light mode.

[mofazhe]

1. Improved button style for this dialog
2. Enable focus highlighting for most input

I removed the outline of the input before because the dark mode looked a bit weird, but now I have improved it.

Please check again.

[flawiddsouza]

Thanks. That looks much better.

You can revert this change:

You can use fill: white or any other color to get the required color for dark mode. The existing svg looks a lot better than the icon from fa.

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The modal footer used to have a slightly darker background color:
Before:

After:

Can you keep that?

You should be able to retain the old css with a little change for dark mode. It had its own css variable called soft-color:

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I want to retain the lighter border color of the context menu:
Before:

After:

When context menus overlap with the borders of the application, I wanted it to pop out a bit. Now the borders blend more together.

That'll be all the changes. Then it should be good for merge.

[flawiddsouza]

One more thing I just noticed:
Before:

After:

The lighter borders looked better for inputs. Can you keep the original here as well?

[mofazhe]

I have made changes to these, please check it.

For soft-color, as an alternative, I have added --modal-footer-background-color in the global style. I think this will better cover future theme modifications and additions.

[flawiddsouza]

Everything seems good now. Thanks for the PR.