Adds nrf52 support

Author: benbrittain

cmd/flash/src/lib.rs

@@ -285,6 +285,7 @@ fn flashcmd(
                     let f3 = regex::Regex::new(r"find target/stm32f3").unwrap();
                     let f4 = regex::Regex::new(r"find target/stm32f4").unwrap();
                     let g0 = regex::Regex::new(r"find target/stm32g0").unwrap();
+                    let nr = regex::Regex::new(r"find target/nrf52").unwrap();
 
                     let mut c: Option<String> = None;
 
@@ -305,6 +306,10 @@ fn flashcmd(
                             c = Some("STM32G030C6Tx".to_string());
                             break;
                         }
+                        if nr.is_match(s) {
+                            c = Some("nrf52840_xxAA".to_string());
+                            break;
+                        }
                     }
 
                     if c.is_none() {