Add XML documentation (#10)

The prior `///` F# documentation blocks were not rendering in IDEs, and parameters were not documented. This change adds complete XML documentation to all (but `Compat`) classes, methods, and functions.

Reviewed-on: #10

src/Postgres/BitBadger.Documents.Postgres.fsproj

@@ -3,10 +3,13 @@
   <PropertyGroup>
     <Description>Use PostgreSQL as a document database</Description>
     <PackageTags>JSON Document PostgreSQL Npgsql</PackageTags>
+    <DocumentationFile>bin\$(Configuration)\$(TargetFramework)\$(AssemblyName).xml</DocumentationFile>
   </PropertyGroup>
 
   <ItemGroup>
     <Compile Include="Library.fs" />
+    <Compile Include="WithProps.fs" />
+    <Compile Include="Functions.fs" />
     <Compile Include="Extensions.fs" />
     <Compile Include="Compat.fs" />
     <None Include="README.md" Pack="true" PackagePath="\" />