Initialize syntax highlighting in all examples

[samuel-williams-shopify]

Summary

• add a shared bootstrap module for example pages
• initialize the 15 examples that were previously missing or incompletely configuring Syntax
• update the example template to use the shared bootstrap
• preserve whitespace and overflow layout before direct <syntax-code> elements finish loading
• add a regression test requiring highlighted examples to initialize Syntax

Verification

• npm test (859 tests)
• npm run format:check
• loaded the Lisp example locally and verified its language and theme assets were requested successfully