Merge pull request 'improvement: fix `cargo doc` invocation warning by making `no_main` conditional' (#2) from ErichDonGubler/blue_pill_base:fix-cargo-doc-warning into master

Reviewed-on: BluePill_Rust/blue_pill_base#2

src/main.rs

@@ -7,7 +7,7 @@
 
 #![deny(unsafe_code)]
 #![no_std]
-#![no_main]
+#![cfg_attr(not(doc), no_main)]
 
 //use panic_halt as _;
 use core::panic::PanicInfo;