explain the commented out Cargo.toml bits

Author: japaric

Cargo.toml

@@ -49,6 +49,8 @@ lto = 'fat'
 opt-level = 3 # <-
 overflow-checks = false # <-
 
+# uncomment this to switch from the crates.io version of defmt to its git version
+# check app-template's README for instructions
 # [patch.crates-io]
 # defmt = { git = "https://github.com/knurling-rs/defmt", rev = "use defmt version reported by `probe-run --version`" }
 # defmt-rtt = { git = "https://github.com/knurling-rs/defmt", rev = "use defmt version reported by `probe-run --version`" }