Add repo structure info (#5931)

Fixes #5683
- Added a repo structure description page in docs

site/content/en/docs/contributing/repo-structure.md

+---
+title: 'Repository structure'
+linkTitle: 'Repository structure'
+weight: 12
+description: 'How to find the components needed'
+---
+
+CVAT stores all its components is a single ("monolithic") repository.
+An explanation of CVAT components is available [here](https://youtu.be/CGOBR5ZmIC0?t=237).
+
+Here is the list of the main directories and files in the repository:
+
+- `./` - Various common files for the repository
+- `.github/` - GutHub configuration files
+- `.vscode/` - VS Code configuration files
+- `components/` - optional server services
+- `cvat/` - server source code
+  - `apps/` - server modules sources
+  - `requirements/` - server Python package requirements
+  - `settings/` - server configurations
+- `cvat-canvas/` - UI package, responsible for the annotation canvas
+- `cvat-canvas3d/` - UI package, responsible for the annotation canvas for 3D
+- `cvat-cli/` - CLI utility
+- `cvat-core/` - UI package, responsible for server interaction
+- `cvat-data/` - UI package, responsible for media data decoding
+- `cvat-sdk/` - Python SDK package
+- `cvat-ui/` - UI package, responsible for UI elements
+- `helm-chart/` - Helm configuration for deployment on Kubernetes
+- `serverless/` - AI models
+- `site/` - Documentation website sources
+  - `assets/` - Media content
+  - `content/` - Documentation pages
+- `supervisord/` - supervisord deployment configuration
+- `tests/` - End-to-end tests
+  - `cypress/` - UI end-to-end tests
+  - `python/` - Tests for server, SDK, CLI and other Python components
+- `utils/` - Additional tools and utility scripts
+  - `dataset_manifest/` - Python library and a tool to create dataset manifest files
+  - `dicom_converter/` - Script to convert DICOM data to CVAT-compatible format
+- `docker-compose*.yml` - Docker Compose local deployment configuration
+- `Dockerfile*` - Docker image descriptions
+- `manage.py` - Django utility to manipulate server components