Update copilot-instructions.md

Author: yuokada

.github/copilot-instructions.md

@@ -1,7 +1,7 @@
-## Prerequisites
-- java 17 or 21
-- quarkus 3.15
-- picoCLI 4.6.1 or higher
-- Apache maven 3.9 or later
+## Coding Conventions
+
+- Use API supported by java 17
+- Use new syntax and features of java 17 if possible
+- In this project, Quarkus 3.15, picoCLI 4.6, Junit 5 and Apache maven 3.9 or later are used
 - Docker 27.0 or later
 - memcached 1.6 or later