docs: README update #9

- Added "How It Works" section in README
- Added "Contributing" section in README (including branch name-convention)

Author: luk-kop

README.md

@@ -2,6 +2,10 @@
 
 [![Python 3.12](https://img.shields.io/badge/python-3.12-blue.svg)](https://www.python.org/downloads/release/python-3120/)
 [![MIT license](https://img.shields.io/badge/License-MIT-blue.svg)](https://lbesson.mit-license.org/)
+[![CI](https://github.com/luk-kop/nmea-gps-emulator/actions/workflows/ci.yml/badge.svg)](https://github.com/luk-kop/nmea-gps-emulator/actions/workflows/ci.yml)
+[![CI Multi-Platform](https://github.com/luk-kop/nmea-gps-emulator/actions/workflows/ci-multiplatform.yml/badge.svg)](https://github.com/luk-kop/nmea-gps-emulator/actions/workflows/ci-multiplatform.yml)
+[![CodeQL](https://github.com/luk-kop/nmea-gps-emulator/actions/workflows/codeql.yml/badge.svg)](https://github.com/luk-kop/nmea-gps-emulator/actions/workflows/codeql.yml)
+[![codecov](https://codecov.io/gh/luk-kop/nmea-gps-emulator/branch/main/graph/badge.svg)](https://codecov.io/gh/luk-kop/nmea-gps-emulator)
 
 The **NMEA-GPS Emulator** is a simple script that emulates a GPS receiver (simulates unit's movement). Data generated by the script are sent to clients in **NMEA 0183** format.
 This script can be useful for testing applications or systems that require some unit's GPS position data.
@@ -48,6 +52,38 @@ $GPVTG,90.0,T,,M,10.5,N,19.4,K*51
 $GPZDA,173124.000,05,11,2021,0,0*50
 ```
 
+***
+## How It Works
+
+The emulator simulates realistic GPS receiver behavior through several key components:
+
+### Position Calculation
+- Uses **pyproj** library for geodetic calculations on the WGS84 ellipsoid
+- Calculates new positions based on current speed, heading, and time elapsed
+- Converts between geographic coordinates (lat/lon) and projected coordinates for accurate distance calculations
+- Updates position every second based on the unit's velocity vector
+
+### NMEA Sentence Generation
+- Generates 8 standard NMEA 0183 sentences with proper formatting
+- Calculates XOR checksums for each sentence to ensure data integrity
+- Simulates realistic GPS data including:
+  - Satellite information (GPGSV) with pseudo-random satellite positions and signal strengths
+  - Dilution of Precision (DOP) values for position accuracy estimation
+  - Time synchronization with system clock
+
+### Threading Architecture
+- **Main thread**: Handles user input for interactive speed/course changes
+- **Worker threads**: Manage client connections and data transmission
+  - TCP Server mode: Accepts up to 10 concurrent client connections
+  - TCP/UDP Stream mode: Maintains persistent connection to specified client
+  - Serial mode: Transmits data via RS-232 serial port
+- Thread-safe communication using events and locks for coordinated shutdown
+
+### Data Transmission
+- Sends complete NMEA sentence sets every second
+- Automatically updates position before each transmission
+- Supports interactive runtime modifications of speed and heading without interrupting data flow
+
 ***
 ## Getting Started
 
@@ -152,3 +188,23 @@ After starting the script correctly, the following prompt should appear in the O
 4 - Quit
 >>>
 ```
+
+***
+## Contributing
+
+Contributions are welcome! When creating a pull request, please ensure your branch name follows the naming convention:
+
+**Valid branch name prefixes:**
+- `feature/` - New features
+- `fix/` or `bugfix/` - Bug fixes
+- `hotfix/` - Urgent fixes
+- `docs/` - Documentation changes
+- `chore/` - Maintenance tasks
+- `refactor/` - Code refactoring
+- `test/` - Test additions or modifications
+- `ci/` - CI/CD changes
+- `release/` - Release preparation
+
+**Example:** `feature/add-nmea-sentence` or `fix/serial-port-timeout`
+
+Pull requests with branch names not following this convention will be rejected by CI validation.