Add source from Pacific Data Hub

[charphi]

API documentation: https://sis-cc.gitlab.io/dotstatsuite-documentation/

SdmxWebSource:

Key	Value
Name	SPC
Description	Pacific Data Hub
Endpoint	https://stats-nsi-stable.pacificdata.org/rest
Website	https://stats.pacificdata.org/?locale=en

[charphi]

Examples:

• Flows: https://stats-nsi-stable.pacificdata.org/rest/dataflow/all/all/latest
• Flow: https://stats-nsi-stable.pacificdata.org/rest/dataflow/all/DF_BOP/latest
• Structure: https://stats-nsi-stable.pacificdata.org/rest/datastructure/SPC/DSD_BOP/1.0?references=children
• Data: https://stats-nsi-stable.pacificdata.org/rest/data/SPC%2CDF_BOP%2C1.0/A..AMTUSD./all

[charphi]

Done in dae3073367cbba3c1c496ea294878ae9194e4105