Update Cargo build for tinysearch

[lspdrz]

The tinysearch fixtures/index.json command in the "Usage" section of the readme isn't working. I think this is because the Cargo build for tinysearch hasn't been changed since the fix in this PR: #154.

When I ran the local project using cargo run fixtures/index.json, the generation worked as expected.

[mre]

Old issue, but this should be resolved now in 0.8.1 if you want to try again.