Feature request: tidy executor

[llucasshenrique]

Request:

Create an tidy executor and migration to add it to projects using '@nx-go/nx-go'.

What it will do:

The executor will run go mod tidy on the application or library "projectRoot".
The migration will be used to add the 'tidy' executor to projects that are using '@nx-go/nx-go'.

Why we need:

Currently to tidy our packages we need to navigate to each project and run go mod tidy this create a problem when we want to split our code in various libraries.

This will open the ability to execute one command to tidy multiple projects using nx run-many -t tidy, or nx affected -t tidy.
Or to use in a single project with nx run project:tidy, or nx tidy project

Current known workarounds:

#107 (comment)