Exercise 1 missing @id annotation

[EmanueleGallone]

Hi, this issue regards the Exercise1.md

To which P4 entity does the ID 16812802 belong to? A table, an action, or something else? What is the corresponding fully qualified name?,

I think there's a missing @id annotation in the main.p4 file. Future releases of the P4Compiler could lead to a mismatch of the ID 16812802, causing some confusion.