frontend: update theming functionality (#123)
* docs: add instructions on theming
* feat: add custom logo function
* feat: update env variables and templates
* fix: apply suggestions
* docs: update theming.md
* docs: formatting
* Update .env-template
Co-authored-by: misspia-cohere <140425731+misspia-cohere@users.noreply.github.com>
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Co-authored-by: misspia-cohere <140425731+misspia-cohere@users.noreply.github.com>
