Fix build instructions, point to Development
Fix build instructions, point to Development

This PR addresses two issues:
- Current build instructions don't work out of the box and lead to errors due to wasm32-unknown-unknown missing.
- The README points to releases for latest artifacts however such releases don't ship the built artifacts so they need to be built from source

Signed-off-by: Víctor Mayoral Vilches <684b52d0ae01c206f1959fcb285dd13757e93b98@gmail.com>

asciinema/asciinema-player,asciinema/asciinema-player