Define filecoin top level capability

[fforbeck]

Define filecoin top level capability so it is easy to delegate all of them at once: e.g. https://github.com/storacha/w3up/blob/a3af22678b45365fa951d88d9251bf6e0d0d65b2/packages/capabilities/src/store.js#L24-L32

Add the top capability (*):

• https://github.com/storacha/w3up/blob/main/packages/capabilities/src/filecoin/storefront.js
• https://github.com/storacha/w3up/blob/a3af22678b45365fa951d88d9251bf6e0d0d65b2/packages/capabilities/src/types.ts#L894