Add net5.0 target

* add it in ImageSharp.csproj
* update Buildscript

.github/workflows/build-and-test.yml

@@ -14,6 +14,18 @@ jobs:
         strategy:
             matrix:
                 options:
+                    - os: ubuntu-latest
+                      framework: net5.0
+                      runtime: -x64
+                      codecov: true
+                    - os: macos-latest
+                      framework: net5.0
+                      runtime: -x64
+                      codecov: false
+                    - os: windows-latest
+                      framework: net5.0
+                      runtime: -x64
+                      codecov: false
                     - os: ubuntu-latest
                       framework: netcoreapp3.1
                       runtime: -x64

src/ImageSharp/ImageSharp.csproj

@@ -12,7 +12,7 @@
     <PackageProjectUrl>$(RepositoryUrl)</PackageProjectUrl>
     <PackageTags>Image Resize Crop Gif Jpg Jpeg Bitmap Png Tga NetCore</PackageTags>
     <Description>A new, fully featured, fully managed, cross-platform, 2D graphics API for .NET</Description>
-    <TargetFrameworks>netcoreapp3.1;netcoreapp2.1;netstandard2.1;netstandard2.0;netstandard1.3;net472</TargetFrameworks>
+    <TargetFrameworks>net5.0;netcoreapp3.1;netcoreapp2.1;netstandard2.1;netstandard2.0;netstandard1.3;net472</TargetFrameworks>
   </PropertyGroup>
 
   <ItemGroup>