[GB-SSD] UK sanctions relating to South Sudan JSON

Gives effect to the UN Security Council's South Sudan sanctions regime, established by resolution 2206 (2015) and extended by resolution 2428 (2018), targeting persons who threaten the peace, stability or security of South Sudan. Designated persons are subject to an asset freeze, and designated individuals are barred from entering or transiting the United Kingdom. The regime also imposes a country-wide embargo on the export of military goods and technology to South Sudan.