Added `RECEIVER_PDF_VIEWER_CONTEXT.md` to the `src` project, documenting the current implementation and behavior of the receiver-side PDF viewing and signing experience in the `EnvelopeGenerator` project.
The document outlines the use of `PDF.js` as the current rendering engine, the planned migration to `DxPdfViewer`, and the functional capabilities that must be preserved. Key features include single-page PDF viewing, navigation, zoom, signature overlays, and metadata validation.
This addition ensures clarity for future development and emphasizes the importance of maintaining existing workflows during the migration or other changes.
