[Feature] Field Indexing and Search Query Parameter

[jmsargent10]

• set up an Atlas Search index for all relevant fields (first name, last name, email, school)
  • for now the collection being used will be the "hacker_applications" collection under the "ApplicantData" database for testing purposes
• update the apiClient.ts file to take in an optional parameter searchQuery? (type string) and include it in the axios request parameters
  • also be sure to update the ApplicantsApiResponse data type in the types.ts file

AC:

• please include screenshots in PR evidencing field indexing!
• the searchQuery parameter has been added