add some readme notes
add some readme notes

meta-rust/meta-rust,cardoe/meta-rust,jmesmon/meta-rust,cardoe/meta-rust,jmesmon/meta-rust,meta-rust/meta-rust,jmesmon/meta-rust,cardoe/meta-rust,jmesmon/meta-rust,meta-rust/meta-rust,meta-rust/meta-rust,starlab-io/meta-rust,cardoe/meta-rust,starlab-io/meta-rust,meta-rust/meta-rust