[google-labs-jules]

This pull request introduces a new tutorial for using Virtual Threads in Spring Boot, matching the current trends in the Java ecosystem (Project Loom). It consists of:

• Enabling virtual threads via spring.threads.virtual.enabled=true.
• Simulating a blocking database I/O within a REST controller.
• Integrating Testcontainers to test the setup.
• Explaining the concepts in an Asciidoc file README.adoc formatted similarly to existing repository submodules.

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PR created automatically by Jules for task 6414381275244446823 started by @rashidi

[google-labs-jules]

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