Created .props file to copy .env files to the publish directory (#138)

* Added `DotEnv.Core.Props` package to the example project

example/DotEnv.Core.Example.csproj

@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
@@ -11,4 +11,8 @@
     <ProjectReference Include="..\src\DotEnv.Core.csproj" />
   </ItemGroup>
 
+  <ItemGroup>
+    <PackageReference Include="DotEnv.Core.Props" Version="1.0.1" />
+  </ItemGroup>
+
 </Project>

props/DotEnv.Core.nuspec

@@ -0,0 +1,29 @@
+<?xml version="1.0"?>
+<package xmlns="http://schemas.microsoft.com/packaging/2010/07/nuspec.xsd">
+    <metadata>
+        <id>DotEnv.Core.Props</id>
+        <version>1.0.1</version>
+        <authors>David Román Amariles</authors>
+        <owners>David Román Amariles</owners>
+        <projectUrl>https://github.com/MrDave1999/dotenv.core</projectUrl>
+        <license type="expression">MIT</license>
+        <readme>README.md</readme>
+        <icon>dotenv-icon-nuget.png</icon>
+        <requireLicenseAcceptance>false</requireLicenseAcceptance>
+        <description>
+          dotenv.core.props is a file that represents a set of properties that will tell MSBuild to copy the .env files 
+          from the project folder to the publish directory.
+        </description>
+		<releaseNotes>
+          - fix: Added .props extension to the build/DotEnv.Core.Props file.
+		</releaseNotes>
+        <copyright>Copyright ©2023 David Román Amariles</copyright>
+        <tags>properties props dotenv env environment variables</tags>
+    </metadata>
+
+    <files>
+        <file src="README.md" target="" />
+        <file src="..\dotenv-icon-nuget.png" target="" />
+        <file src="build\**" target="build" />
+    </files>
+</package>

props/README.md

@@ -0,0 +1,26 @@
+**DotEnv.Core.Props** is a file that represents a set of properties that will tell MSBuild to copy the .env files from the project folder to the publish directory.
+
+This .props file **excludes** the following sample .env files:
+- `.env.example`
+- `example.env`
+- `.env.sample`
+- `sample.env`
+- `.env.template`
+- `template.env`
+
+## Installation
+
+Run the following command from the terminal:
+```
+dotnet add package DotEnv.Core.Props
+```
+
+## How to use it?
+
+The .props file does not need to be used directly, simply run the `dotnet publish` command and MSBuild will copy the .env files to the publish directory.
+
+Remember that .env files must follow either of these two conventions:
+- `.env.{name}` (e.g., .env.config).
+- `{name}.env` (e.g., config.env).
+
+Following these conventions is necessary for MSBuild to know which file to copy to the publish directory.

props/build/DotEnv.Core.Props.props

@@ -0,0 +1,31 @@
+<Project>
+
+  <PropertyGroup>
+    <!-- 
+      Redefine the DefaultItemExcludes property to exclude the folders as ./bin, ./obj and .env files of samples. 
+      This also excludes sample .env files that are located in subdirectories of the project folder.
+    -->
+    <DefaultItemExcludes>
+      $(DefaultItemExcludes);
+      **\.env.example;
+      **\example.env;
+      **\.env.sample;
+      **\sample.env;
+      **\.env.template;
+      **\template.env
+    </DefaultItemExcludes>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <!-- 
+      Copy all the .env files to the publish directory (except for sample files). It will also copy .env files that are in subdirectories.
+      The publish directory contains the assemblies ready for deployment to a hosting system (for example, a server, PC, laptop) for execution.
+    -->
+    <Content 
+      Include="**\*.env*" 
+      CopyToPublishDirectory="PreserveNewest" 
+      Exclude="$(DefaultItemExcludes)" 
+    />
+  </ItemGroup>
+
+</Project>