chore: add avif format as image

[manniL]

AVIF, a new image compression format, will be supported in the next Chrome version and is supported behind a flag in FireFox (source). We should add it to our default webpack config so users can utilize the format!

Types of changes

• Bug fix (a non-breaking change which fixes an issue)
• New feature (a non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly. (PR: #)
• I have added tests to cover my changes (if not applicable, please state why)
• All new and existing tests are passing.

[codecov-commenter]

Codecov Report

Merging #7961 into dev will not change coverage.
The diff coverage is 0.00%.

@@           Coverage Diff           @@
##              dev    #7961   +/-   ##
=======================================
  Coverage   68.92%   68.92%           
=======================================
  Files          91       91           
  Lines        3846     3846           
  Branches     1041     1041           
=======================================
  Hits         2651     2651           
  Misses        971      971           
  Partials      224      224           

Flag	Coverage Δ
#unittests	68.92% <0.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
packages/vue-renderer/src/renderers/spa.js	0.00% <0.00%> (ø)
packages/webpack/src/config/base.js	64.63% <ø> (ø)

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[phartikainen]

Took me....a loooongggggggg time to figure out why my webpack config would not work after 2.14.3.