String-based API support

Crowdin has recently released a new type of projects - **String-based**.

In string-based projects, the focus is on managing translatable content as individual strings rather than source files. In this project type, after uploading source files, Crowdin parses them into source strings. Unlike file-based projects, source files aren’t stored, and the emphasis is on managing the content at the string level. This approach is beneficial when dealing with projects that involve continuous content updates, dynamic content, or where a string-oriented structure is preferred.

As a result, the API differs a bit from the file-based projects. Most of the endpoints are the same, but some endpoints have different parameters or return different responses, some endpoints are not available at all, and some new endpoints are available only for string-based projects.

We should update the API clients to support string-based projects as well.

**References:**

- [Crowdin API v2 Reference (String-based)](https://developer.crowdin.com/api/v2/string-based/)
- [Crowdin API v2 Reference (File-based)](https://developer.crowdin.com/api/v2/)

**It has been implemented for the following clients:**

- https://github.com/crowdin/crowdin-api-client-js/pull/328
- https://github.com/crowdin/crowdin-api-client-java/pull/212