Add default SVG silhouette icon

[ekdahl]

Should not affect supplied themes, until "content" CSS property is unset for parent element. Suggestion for #5049.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 35.20%. Comparing base (2b3a3e6) to head (ed12be6).

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #5088   +/-   ##
=========================================
  Coverage     35.20%   35.20%           
  Complexity    11236    11236           
=========================================
  Files          1159     1159           
  Lines         48108    48108           
=========================================
  Hits          16937    16937           
  Misses        31171    31171           

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[fisharebest]

I like the idea of using the SVG icons for the silhouette image.

Do you think the "solid" icon is better for this? https://fontawesome.com/icons/user?f=classic&s=solid

We should use the same image in the chart boxes.

Perhaps create a new view (e.g. resources/views/silhouette.phtml) that we can use for both.

I see that the code for thumbnail images / silhouettes is slightly different for chartboxes and the individual page. I need to make this consistent.