change output of rgb2name to csv string

[mdieperink]

Change the output of rgb2name to CSV string. So it's possible to convert the output to a list again after calling the function.
Also remove a linebreak from the output.

To test:

{% from 'color_multi_tool.jinja' import rgb2name %}
{%- set rgbl = (254,159,70) | list %}
{{ rgb2name(40, rgbl) }}
{{ rgb2name(40, rgbl).split(',') }}
{{ rgb2name(40, rgbl).split(',')[0] }}

output:

coral,goldenrod,sandybrown
['coral', 'goldenrod', 'sandybrown']
coral