refactor: Add wasm support

[dariusc93]

This PR introduce basic WASM support, allowing one to compile and run while targeting wasm32-unknown-unknown

Relates to #6

Note:

• Due to Repo current design, it may not be compatible with some wasm implementation due to objects not supporting Send or Sync. A workaround for that is to have a single future that handles access to the data while using channels to communicate. In a later version, Repo may be refactored to support stores without Sync and Send.
• indexeddb repo would have to be manually initialized
  • for now the blockstore has a basic implementation. The datastore will be implemented later