Adding experimental UV Index support for weather module (#3108)

This pr adds (config.js toggleable) showUV_Index to the hourly and
current weather modules, with right now only openmeteo configured to
supply the data. Other providers could have support too by adding
`uv_index` to current and hourly.

For example the current weather looks like
![image](https://github.com/MichMich/MagicMirror/assets/124401812/00fdf5db-c0d5-4797-9a31-1d72dd970d26)
positioned after sunset in the top row.



The following "hacks" are included and could be fixed to make it
cleaner, but the functionality is wanted and it works without problem.
- To hide entries where the UV Index is 0 i added an if statement to the
`hourly.njk` which is not how precipitation is handled.
The following are minor things that might not need fixing:
- The forecast option does not have UV support. This might not be
relevant since UV changes throughout the day but i tried to implement a
"max_UV" to openmeteo.js, but am not confident enough in JS to
accomplish that.
- The UV Icon is wi-hot and manually added to the `.njk`'s. This could
be made changeable by a config but does not seem relevant since wi-hot
is not used by anything else as far as i can tell.

---------

Co-authored-by: veeck <michael@veeck.de>

modules/default/weather/current.njk

@@ -28,6 +28,12 @@
                     {% endif %}
                 </span>
             {% endif %}
+            {% if config.showUVIndex %}
+                    <td class="align-right bright uv-index">
+                    <div class="wi dimmed wi-hot"></div>
+                        {{ current.uv_index }}
+                    </td>
+            {% endif %}
         </div>
     {% endif %}
     <div class="large light">
@@ -61,12 +67,12 @@
                     {{ "FEELS" | translate({DEGREE: current.feelsLike() | roundValue | unit("temperature") | decimalSymbol }) }}
                 </span><br/>
             {% endif %}
-            {% if config.showPrecipitationAmount and current.precipitationAmount %}           
+            {% if config.showPrecipitationAmount and current.precipitationAmount %}
                 <span class="dimmed">
                     <span class="precipitationLeadText">{{ "PRECIP_AMOUNT" | translate }}</span> {{ current.precipitationAmount | unit("precip", current.precipitationUnits) }}
                 </span><br/>
             {% endif %}
-            {% if config.showPrecipitationProbability and current.precipitationProbability  %}           
+            {% if config.showPrecipitationProbability and current.precipitationProbability  %}
                 <span class="dimmed">
                     <span class="precipitationLeadText">{{ "PRECIP_POP" | translate }}</span> {{ current.precipitationProbability }}%
                 </span>