Create CONTRIBUTING.md

Author: EndrII

CONTRIBUTING.md

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+# Contributing in to EeasySSL 
+This is a wrap library for the Qt developers. So if you think that is a good library, and you use it in your projects - you can add new improvements and create a pull request with new features.
+
+## What can you do for this Library ? 
+1. You can add a support of new encryption algorithms 
+2. You can implement new certificate generator.
+
+## Adding new implementation of crypto algorithms
+All Algorithms must be pass simple test. Encrypt, decrypt short and long data arrays. This simple test already implemented, and you just need to add it into main test file. 
+
+### Example
+Adding supporting RSA algorithm to this library. 
+
+1. Create implementation of the iCrypto interface.
+   ```cpp
+
+   #include "icrypto.h"
+
+     /**
+     * @brief The RSASSL class This is wrapper for RSA algorithm of openssl 3.0 libraryry.
+     */
+    class EASYSSL_EXPORT RSASSL: public EasySSL::ICrypto {
+  
+      // override main methods of the interface.
+      EVP_PKEY *makeRawKeys() const override;
+      Features supportedFeatures() const override;
+      QSsl::KeyAlgorithm keyAlgorithm() const override;
+      QByteArray signMessage(const QByteArray &inputData, const QByteArray &key) const override;
+      bool checkSign(const QByteArray &inputData, const QByteArray &signature, const QByteArray &key) const override;
+      QByteArray decrypt(const QByteArray &message, const QByteArray &key) override;
+      QByteArray encrypt(const QByteArray &message, const QByteArray &key) override;
+  
+    }
+   ```
+Full implementation of the RSA  you can see here.
+
+2. Add your class to the tests Using The Template class "[CryptoTest](https://github.com/QuasarApp/easyssl/blob/main/tests/units/cryptotest.h)". See The [tstMain.cpp](https://github.com/QuasarApp/easyssl/blob/main/tests/tstMain.cpp) file
+``` cpp
+    TestCase(cryptoTestRSA, CryptoTest<EasySSL::RSASSL>)
+```
+
+## Adding new implementation of Certificate generator. 
+
+1. Create implementation of the iCrypto interface. And override the create method.
+```cpp
+  /**
+   * @brief The X509 class This is wrapper of the ssl objects.
+   */
+  class EASYSSL_EXPORT X509: public ICertificate
+  {
+  public:
+      X509(const QSharedPointer<ICrypto>& generator);
+  
+      // ICertificate interface
+  public:
+      SelfSignedSertificate create(const SslSrtData& certificateData) const override;
+  };
+```
+
+Full implementation of x509 certificate format you can see here.
+
+2. Add your class to the tests Using The Template class "[CrtTest]()". See The [tstMain.cpp](https://github.com/QuasarApp/easyssl/blob/main/tests/tstMain.cpp) file
+
+```cpp
+  #include "crttest.h"
+
+  using CrtTestX509ECDSA = CrtTest<EasySSL::X509, EasySSL::ECDSASSL>;
+  TestCase(crtTestX509ECDSA, CrtTestX509ECDSA)
+
+```
+
+## Extra rools
+1. All shared tools or useful functions located on the EasySSLUtils class.
+2. All implementation must contains goxygen xml comments (documentation)
+
+
+# Thank you  
+