minor symfony#17650 Add YAML encoder to serializer diagram (l-vo)

This PR was merged into the 5.4 branch.

Discussion
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Add YAML encoder to serializer diagram

Add YAML encoder to serializer diagram.

`@javiereguiluz` the font is not the same because I don't have the font you originally used, do you have it ?

Commits
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a0ecf18 Add YAML encoder to serializer diagram

Author: javiereguiluz