message: [pdsl] Add eDSL link to README
diff: **IMPORTANT NOTE:** WORK IN PROGRESS! Do not expect this to be working.
  -Write WebAssembly based smart contracts in the Rust programming language.
  +An [eDSL](https://wiki.haskell.org/Embedded_domain_specific_language) to write WebAssembly based smart contracts in the Rust programming language.
  - [`pdsl-core` API documentation](https://robbepop.github.io/pdsl/pdsl_core/index.html).
  