Add Interpeer to the signatories

[jfinkhaeuser]

Changes proposed in this pull request:

• see subject

Propagation of Changes

Identify where of the following the proposed changes need to be propagated, and include the relevant pull request where appropriate:

• [ ] The DPGA website contains https://digitalpublicgoods.net/standard/ which needs to be updated manually matching the contents of standard.md.
• [ ] The DPGA website also contains the submission guide which needs to be updated manually.
• [ ] The unicef/publicgoods-candidates repository needs the following to be updated:
  • [ ] the nominee-schema.json
  • [ ] the screening-schema.json
  • [ ] propagate any changes to all encoded nominees and digital public goods.
  • Link to the corresponding pull request: unicef/publicgoods-candidates#
• [ ] The Submission Form through the unicef/publicgoods-submission repository, and its corresponding schema.js
  • Link to the corresponding pull request:
• [ ] The Eligibility Form through the unicef/publicgoods-scripts repository, by editing quizQuestions.js
  • Link to the corresponding pull request: