Write an article about the Wasm code instrumentation

[shamilsan]

• Source: https://github.com/gear-tech/gear-tech.github.io/blob/master/src/protocol/wasm-instrumentation.md
• Output: https://gear.rs/protocol/wasm-instrumentation.html

Need to write what is done during Wasm instrumentation (after loading the code but before the module instantiation). It would be great to provide links to the chunks of source code (we can use some release tag e.g. v1.0.3).