prerequisites.md: note about <id>
prerequisites.md: note about <id>

JetBrains/intellij-sdk-docs,artspb/intellij-sdk-docs,artspb/intellij-sdk-docs,artspb/intellij-sdk-docs,artspb/intellij-sdk-docs,JetBrains/intellij-sdk-docs,JetBrains/intellij-sdk-docs