Add contributor guides (`CONTRIBUTING.md`)

[SgtPooki]

need to define our contributing guidelines, or find an existing example to copy

[AlexxNica]

@SgtPooki any specific examples you want to use?

Here are some that I suggest we can use as inspiration:

• github/docs/CONTRIBUTING.md
• github/opensource.guide/CONTRIBUTING.md
• microsoft/TypeScript/CONTRIBUTING.md
• microsoft/vscode/CONTRIBUTING.md
• kubernetes/kubernetes/CONTRIBUTING.md

TypeScript and vscode are more detailed and have sections specific to coding. They also have wikis for more in-depth guides:

• https://github.com/microsoft/TypeScript/wiki/Contributing-to-TypeScript
• https://github.com/microsoft/vscode/wiki/How-to-Contribute

Another example is Kubernetes' contributing docs, which is very comprehensive. IMO we probably don't need the same governance processes involved in Kubernetes right now, so we can just use it as inspiration and get some pieces here and there that are relevant to our project, but not everything.

[SgtPooki]

I think leaning more into the existing contributing docs for ipfs repos makes the most sense, but those are great for ideas for improvements.

Some existing contributing docs:

• https://github.com/ipfs/ipfs-companion/blob/eeaa0838f920f5a36289818d9f885dcf075ca2e0/docs/CONTRIBUTING.md
• https://github.com/ipfs/community/blob/e0812a37d7a611bbf1f3b37b0bd00c017f98da8f/CONTRIBUTING.md
• https://github.com/ipfs/community/blob/e0812a37d7a611bbf1f3b37b0bd00c017f98da8f/CONTRIBUTING_JS.md
• https://github.com/ipfs/kubo/blob/ef866a1400b3b2861e5e8b6cc9edc8633b890a0a/CONTRIBUTING.md
• https://github.com/ipfs/js-ipfs/blob/6870873f0696bb5d8d91fce4a4ef1f7420443993/packages/ipfs/CONTRIBUTING.md

I think a mix of the following two would be good:

• https://github.com/ipfs/community/blob/master/CONTRIBUTING_JS.md
• https://github.com/ipfs/js-ipfs/blob/master/CONTRIBUTING.md