Update README.md

Author: Maxyee

jwtauthcore/README.md

@@ -42,3 +42,101 @@ namespace jwtauthcore.Controllers
 
 ```
 
+Final Look of the Authenticate Mehtod
+
+```cs
+[AllowAnonymous]   // everybody can call this mehtod but rest of the method is authorized.
+[HttpPost("authenticate")]
+public IActionResult Authenticate([FromBody] UserCred userCred)
+{
+    var token = jwtAuthenticationManager.Authenticate(userCred.Username, userCred.Password);
+    if(token == null)
+    {
+        return Unauthorized();
+    }
+    return Ok(token);
+}
+
+```
+
+here is the authenticate method code from `JwtAuthenticationManager` file
+
+```cs
+public string Authenticate(string username, string password)
+{
+
+    if(!users.Any(u => u.Key == username && u.Value == password))
+    {
+        return null;
+    }
+
+
+    var tokenHandler = new JwtSecurityTokenHandler();
+    var tokenKey = Encoding.ASCII.GetBytes(key); 
+
+    var tokenDescriptor = new SecurityTokenDescriptor
+    {
+        Subject = new ClaimsIdentity(new Claim[]
+        {
+            new Claim(ClaimTypes.Name, username)
+        }),    
+        Expires = DateTime.UtcNow.AddHours(1), 
+        SigningCredentials = 
+            new SigningCredentials(
+                new SymmetricSecurityKey(tokenKey),
+                SecurityAlgorithms.HmacSha256Signature) 
+    };
+    var token = tokenHandler.CreateToken(tokenDescriptor);
+    return tokenHandler.WriteToken(token);
+}
+
+```
+
+And the Interface `IJwtAuthenticationManager` where I mentioned our authenticate mehtod.
+
+```cs
+namespace jwtauthcore.Interface
+{
+    public interface IJwtAuthenticationManager
+    {
+        string Authenticate(string username, string password);
+    }
+}
+
+```
+
+Finally the dependency Injection to `Startup.cs` file
+
+```cs
+public void ConfigureServices(IServiceCollection services)
+{
+    services.AddControllers();
+
+
+    var key = "this is test key";
+
+    services.AddAuthentication(x => 
+    {
+        x.DefaultAuthenticateScheme = JwtBearerDefaults.AuthenticationScheme;   
+        x.DefaultChallengeScheme = JwtBearerDefaults.AuthenticationScheme; 
+    }).AddJwtBearer(x => 
+    {
+        x.RequireHttpsMetadata = false;
+        x.SaveToken = true;
+        x.TokenValidationParameters = new TokenValidationParameters 
+        {
+            ValidateIssuerSigningKey = true,
+            IssuerSigningKey = new SymmetricSecurityKey(Encoding.ASCII.GetBytes(key)),
+            ValidateIssuer = false,
+            ValidateAudience = false
+        };
+    });
+    services.AddSingleton<IJwtAuthenticationManager>(new JwtAuthenticationManager(key));
+}
+
+```
+
+### Testing with PostMan
+
+
+