Only use yarn, fix comments

[Thoralf-M]

Description of change

Only use yarn so we don't have multiple lock files. Changed the examples installation to use yarn link, because otherwise it always failed with

error: current package believes it's in a workspace when it's not:
current:   /iota-sdk/bindings/nodejs/examples/node_modules/@iota/sdk/Cargo.toml
workspace: /iota-sdk/Cargo.toml

Also updated wrong comments.

Links to any relevant issues

Closes #1949
Closes #1925

Type of change

• Enhancement (a non-breaking change which adds functionality)
• Documentation Fix

How the change has been tested

Running installation commands and an example afterwards

[thibault-martinez]

Can you check the READMEs pls? I think they may reference npm