Closes #49: add `get_terms()` from `admiral.test` #60

Job	Run time
Documentation	0s
Render README	0s
Validation	0s
Check / (4.1)	2m 16s
Check / (4.2)	2m 25s
Check / (4.3)	2m 55s
Code Coverage / Get R version	1s
Links / Validate Links	6s
Lint / Get R version	2s
Man Pages / Get R version	1s
Spelling / Get R version	1s
Code Style / Get R version	1s
Man Pages / Roxygen	1m 15s
Code Style / Code Style	1m 21s
Code Coverage / Test Coverage	2m 10s
Lint / Lint	1m 13s
Spelling / Spellcheck	1m 29s
Code Coverage / Generate badge for coverage	4s
	15m 20s

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