Provide build script for compiling contracts instead of uploading wasm files

[clearloop]

Problem

ref #143 , the wasm files are big as well, for example https://github.com/gear-foundation/dapps/tree/master/frontend/apps/escrow/src/assets/wasm, plus the wasm files are changing while the development of contracts, so a compile script before dev makes sense tbh

Solution

provide a script in package.json like compile to compile the target contract and cp the meta.wasm to the expected place on development

[Madib036]