Use relative link paths for the GNO website

[zivkovicmilos]

Description

This PR simply modifies the HOME.md file in the gno website module to utilize relative link paths, instead of hardcoded link paths.

As pointed out in #458, spinning up a local version of the website will link to the testnet, and not the local running instance, on the homepage.

Additionally, a build step was added to the all directive in the Makefile, so existing READMEs are valid - the gnofaucet binary is not being built in the build folder, but the README on the faucet assumes it is.

Changes include

• Bugfix (non-breaking change that solves an issue)
• Hotfix (change that solves an urgent issue, and requires immediate attention)
• New feature (non-breaking change that adds functionality)
• Breaking change (change that is not backwards-compatible and/or changes current functionality)

Checklist (for contributors)

• I have assigned this PR to myself
• I have added at least 1 reviewer
• I have added the relevant labels
• I have updated the official documentation
• I have added sufficient documentation in code

Testing

• I have tested this code with the official test suite
• I have tested this code manually

Manual tests

Deployed the website using the ./build/website command and checked that links are relative instead of absolute.