Added schema for radiohound spectrum data files

[lucaspar]

node ./cli.js check --schema-name=radiohound-v0.json

===== VALIDATE PRECONDITIONS =====
✔️ Directory structure conforms to expected layout
✔️ catalog.json validates against its schema
✔️ catalog.json has no fields that break guidelines
✔️ catalog.json has no duplicate "fileMatch" values
✔️ catalog.json has no invalid schema URLs
✔️ schema-validation.jsonc validates against its schema
✔️ schema-validation.jsonc has no invalid schema names
✔️ schema-validation.jsonc has no invalid schema URLs
✔️ schema-validation.jsonc has no invalid skiptest[] entries
===== VALIDATE SCHEMAS =====
✔️ Completed "pre-checks"
✔️ Completed "Ajv validation"
===== REPORT =====
Out of 1448 TOTAL schemas:
- 664 (46%) are SchemaStore URLs
- 784 (54%) are External URLs

Out of 666 TESTED schemas:
- 276 (41%) are validated with Ajv's strict mode
- 179 (27%) do not have tests.
- 551 (83%) do not have negative tests.
Out of 1 TESTED schemas:
- Total  2020-12: 0
- Total  2019-09: 0
- Total draft-07: 1
- Total draft-06: 0
- Total draft-04: 0
- Total draft-03: 0

[github-actions]

Thanks for the PR!

This section of the codebase is owned by @madskristensen and @hyperupcall - if they write a comment saying "LGTM" then it will be merged.