New xUSDT theme created.

[YegorSan]

This PR is related to #2664 issue.

Motivation

New layout for xUSDT theme was needed.

Changelog

Enhancements

Created a new theme for xUSDT:

And dark mode:

Checklist for your PR

• I added an entry to CHANGELOG.md with this PR
• If I added new functionality, I added tests covering it.
• If I fixed a bug, I added a regression test to prevent the bug from silently reappearing again.
• I checked whether I should update the docs and did so if necessary
• If I added/changed/removed ENV var, I should update the list of env vars in https://github.com/poanetwork/blockscout/blob/master/docs/env-variables.md to reflect changes in the table here https://poanetwork.github.io/blockscout/#/env-variables?id=blockscout-env-variables. I've set master in the Version column.
• If I add new indices into DB, I checked, that they don't redundant with PGHero or other tools

[YegorSan]

@vbaranov Hello Victor. I want to clarify one question. As far as I can see , logic for rendering logo written in embedded elixir syntax:

<img class="navbar-logo" id="navbar-logo" src="<%= logo() %>" alt="<%= subnetwork_title() %>" />

I've created new theme and uploaded logos, please confirm, that no additional steps must be performed from my end. Thank's in advance.

[vbaranov]

@YegorSan

You forgot to add a commented non-critical css to ./assets/css/theme/_variables-non-critical.scss

Question: You didn't provide updates for network selector to support this instance. Is it implied to add this chain to the network menu? if yes, some elements are missing:

• network icon for network selector
• css class for icon
• preload of that icon in ./assets/css/_images-preload.scss

[vbaranov]

@YegorSan in addition to my review, CHANGELOG entry is missing

[YegorSan]

@vbaranov Hello. You are absolutely right. I've just created the new theme, but didn't add any additional changes to network selector yet, as it wasn't mentioned in this issue. Let me work on it right now. I'll take a further look and provide an update shortly.

[YegorSan]

@vbaranov I've added new icons in styles for xUSDT, commented line to non-critical css, style for preload and style for icon. Please review. Thank you in advance.

[vbaranov]

@YegorSan please change the class name from &-xusdt-mainnet to &-xusdt-chain to conform it with xDai Chain

[YegorSan]

@vbaranov Please give me a few minutes.

[YegorSan]

@vbaranov Done. Please check.

[vbaranov]

@YegorSan looks good now