Refactor files for more modularity and easy of adding more

[hacdias]

As I was making #73, I had the idea of restructuring the directories in the following way:

• bin/ - as it is right now.
• src/
  • index.js - move from the root.
  • dnslink/
    • cloudflare.js
    • sth-else.js
  • pinners/
    • infura.js
    • pinata.js
    • ipfs-cluster.js
    • sth-else.js

From dnslink, all files would export the same api:

updateSomethingDns(options)

From pinners, all files would export the same api:

// Setup Pinner
const pinner = setupPinnerName(options)

// Pin from file system
const hash = await pinner.pin(dir, options)

// Pin hash
await pinner.pinHash(hash, options)

Otherwise:

// Setup Pinner
const pin = setupPinnerName(options)

// Pin from file system
const hash = await pin(dir, options)