How to add custom CSS code in the backend level and create new docker image

Thanks for the response. I have created own plugin, the plugin and setting.yml code is below.

plugin.rb

# name: my-theme
# about: CSS theme
# version: 0.1
# authors: Muthukkumar

register_asset 'stylesheets/common.scss'

setting.yml

plugins:
  awesomeness_enabled:
    default: true
    client: true
  awesomeness_max_volume:
    default: 10
    client: true

With this code the css file are working fine like I can able to see the different themes but when I click the plugin button I am getting the error “Error while trying to load”.
console:

[object Error]: {description: "Can't hydrate plugin without an id", message: "Can't hydrate plugin without an id", stack: "Error: Can't hydrate plugin without an id at _hydrate (http://mydomain.cloudapp.azure.com/assets/application-191c740da68414e64ef64eca7583598eb54021aa742309160a164d8f601e141f.js:9:541) at Anonymous function (http://mydomain.cloudapp.azure.com/assets/application-191c740da68414e64ef64eca7583598eb54021aa742309160a164d8f601e141f.js:8:31086) at Array.prototype.map (native code) at _resultSet (http://mydomain.cloudapp.azure.com/assets/application-191c740da68414e64ef64eca7583598eb54021aa742309160a164d8f601e141f.js:8:31063)

And the logo also not getting changed. Could you please help me on that I have tried to find the solution but no luck.

Many thanks in advance.