Improve PreJoin Component and add custom participant placeholders - #1129

Unexpected non-whitespace character after JSON at position 324 (line 21 column 1)

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: andresz1/size-limit-action@94bc357df29c36c8f8d50ea497c3e225c3c95d1d. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/