Add Contribution guide

[imaginator]

The aim is that you can point future contributors to this and they can add documentation.

Should include:

• tone and voice instructions
• address persona needs
• don't assume linux / support other OS's
• instructions for liquid AND bitcoin
• concise and to the point
• just one working example / don't confuse with multiple methods
• anything else you have picked up

Also include all the AI prompts for checking the contributions are compliant with the above and any other requirements.

[imaginator]

please also include in the contributing guide - no possessives. Often the documentation refers to "our lending contract" or "we...."

1. Focus on the Product, Not the People:

Instead of saying "our lending contract," name the contract itself or the system managing it.

• Avoid: "Our lending contract calculates interest daily."
• Better: "The Lending Contract calculates interest daily."

2. Use Imperative or Active Voice

Instead of saying what "we" will do, describe what the system does or what the user should do.

• Avoid: "We will add the funds to your account."
• Better: "The system adds the funds to the account" or "Funds are credited to the account."

[schoen]

I went through and removed a lot of the existing our/we references in the documentation on the site:

3bd5737