Converted src/categories/topics from JS to TS

[shahad1307]

The issue (src/categories/topics.js) has been addressed by translating the code from javascript to typescript (src/categories/topics.ts) that include creating type interface so that the code be translated correctly to typescript code orientation. All the implemented changes in topics.ts file has been tested by passing both lines "npm run lint" and "npm run test" and the last test is to have a green check in green when pulling in github.
fixed #64

[coveralls]

Pull Request Test Coverage Report for Build 6027947907

• 64 of 70 (91.43%) changed or added relevant lines in 3 files are covered.
• 8 unchanged lines in 4 files lost coverage.
• Overall coverage decreased (-0.03%) to 84.95%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/social.js	15	16	93.75%
src/controllers/composer.js	35	40	87.5%

Files with Coverage Reduction	New Missed Lines	%
src/groups/join.js	1	92.05%
src/messaging/notifications.js	1	96.55%
src/database/mongo/hash.js	2	88.07%
src/categories/topics.js	4	87.94%

Totals
Change from base Build 5912059056:	-0.03%
Covered Lines:	22574
Relevant Lines:	25331

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💛 - Coveralls