Hello, I get this Rust errors when compiling:

Compiling clara v0.1.0 (/ev/clara-lang)
error[E0554]: #![feature] may not be used on the stable release channel
--> src/lib.rs:1:1
|
1 | #![feature(box_patterns)]
| ^^^^^^^^^^^^^^^^^^^^^^^^^

error[E0554]: #![feature] may not be used on the stable release channel
--> src/lib.rs:3:1
|
3 | #![feature(concat_bytes)]
| ^^^^^^^^^^^^^^^^^^^^^^^^^

error[E0554]: #![feature] may not be used on the stable release channel
--> src/lib.rs:3:12
|
3 | #![feature(concat_bytes)]
| ^^^^^^^^^^^^

For more information about this error, try rustc --explain E0554.
error: could not compile clara due to 3 previous errors
warning: build failed, waiting for other jobs to finish...

Can the source be adapted for the stable release as well? I am using rust 1.61.0.