Update voice dialog bubble color possibility

[dhoeben]

Added two css variables, with the posibility to let users change the conversation message bubble. This is a fix in case a black/white theme is used. If the variables are not in line with Home Assistant variable names, feel free to change.

First time using GitHubt, I'm sorry if I did something wrong.

Proposed change

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New feature (thank you!)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Example configuration

  theme:
    primary-color: rgb(220, 221, 221)
    primary-background-color: rgb(22, 22, 22)
    secondary-background-color: rgb(22, 22, 22)
    divider-color: rgb(22, 23, 24)
    
    primary-text-color: rgb(220, 221, 221)
    secondary-text-color: rgb(100,100,100)

    # Newly added to theme.yaml:
    primary-conversation-color: red
    secondary-conversation-color: blue

Additional information

• This PR fixes or closes issue: fixes
• This PR is related to issue or discussion: https://community.home-assistant.io/t/specific-color-variable-for-assist-dialog/718137
• Link to documentation pull request:

Checklist

• The code change is tested and works locally.
• There is no commented out code in this PR.
• Tests have been added to verify that the new code works.

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated for www.home-assistant.io

[dhoeben]

ok