Build failures for large images

[ohlr]

2020-07-07T10:45:19.681Z [WARNING]: error There was an error in your GraphQL query:
                                    Unexpected error value: "failed to process https://images.prismic.io/....png\nTimeoutError: Timeout awaiting 'request' for 30000ms"
2020-07-07T10:45:19.694Z [INFO]: not finished run queries - 98.170s
2020-07-07T10:45:19.696Z [INFO]: not finished Generating image thumbnails - 33.602s
2020-07-07T10:45:21.664Z [WARNING]: (sharp:2089): GLib-CRITICAL **: 10:45:21.664: g_hash_table_lookup: assertion 'hash_table != NULL' failed
2020-07-07T10:45:23.401Z [WARNING]: (sharp:2089): GLib-CRITICAL **: 10:45:23.401: g_hash_table_lookup: assertion 'hash_table != NULL' failed
2020-07-07T10:45:23.658Z [WARNING]: (sharp:2089): GLib-CRITICAL **: 10:45:23.658: g_hash_table_lookup: assertion 'hash_table != NULL' failed
2020-07-07T10:45:23.763Z [WARNING]: error Command failed with exit code 1.
2020-07-07T10:45:23.763Z [INFO]: info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.
2020-07-07T10:45:23.768Z [ERROR]: !!! Build failed
2020-07-07T10:45:23.769Z [ERROR]: !!! Non-Zero Exit Code detected

Using gatsby image I see builds failing with large images.

Potential fix: #188 / increase timeout