Add greek language translation (#4462)

Thank you for your contribution

Author: asfyra

CSharp/Library/Microsoft.Bot.Builder/Microsoft.Bot.Builder.csproj

@@ -205,6 +205,7 @@
     </EmbeddedResource>
     <EmbeddedResource Include="Resource\Resources.de-DE.resx" />
     <EmbeddedResource Include="Resource\Resources.cs.resx" />
+    <EmbeddedResource Include="Resource\Resources.el.resx" />
     <EmbeddedResource Include="Resource\Resources.pt-BR.resx">
       <SubType>Designer</SubType>
     </EmbeddedResource>
@@ -227,6 +228,9 @@
     <XliffResource Include="MultilingualResources\Microsoft.Bot.Builder.ar.xlf" />
     <XliffResource Include="MultilingualResources\Microsoft.Bot.Builder.de-DE.xlf" />
     <XliffResource Include="MultilingualResources\Microsoft.Bot.Builder.cs.xlf" />
+    <XliffResource Include="MultilingualResources\Microsoft.Bot.Builder.el.xlf">
+      <SubType>Designer</SubType>
+    </XliffResource>
     <XliffResource Include="MultilingualResources\Microsoft.Bot.Builder.pt-BR.xlf" />
     <XliffResource Include="MultilingualResources\Microsoft.Bot.Builder.en.xlf" />
     <XliffResource Include="MultilingualResources\Microsoft.Bot.Builder.es.xlf">