Implement proper internationalization in the New Frontend

[mcserep]

The current approach for the New Frontend is to store the UI phrases as enum values. While currently only the English language is supported in CodeCompass and we have no near future plans for supporting other languages, it is not really a robust solution and is not really better than hard coding the English texts in the UI code.

E.g.:

export enum SearchMethods {
  EXPRESSION = 'Search by expression',
  FILE_REGEX = 'File name filter regex',
  PATH_REGEX = 'Path filter regex',
}

It could be a much solution to place these into real translation files and use react-i18next for example for internationalization.