Update dockerfile

Dockerfile

@@ -1,8 +1,9 @@
 # Build
-FROM mcr.microsoft.com/dotnet/core/sdk:3.0 AS build
+FROM mcr.microsoft.com/dotnet/core/sdk:3.1 AS build
 WORKDIR /src
 
 COPY favicon.ico ./
+COPY DiscordChatExporter.props ./
 
 COPY DiscordChatExporter.Core.Markdown DiscordChatExporter.Core.Markdown
 COPY DiscordChatExporter.Core.Models DiscordChatExporter.Core.Models
@@ -13,7 +14,7 @@ COPY DiscordChatExporter.Cli DiscordChatExporter.Cli
 RUN dotnet publish DiscordChatExporter.Cli -o DiscordChatExporter.Cli/publish -c Release
 
 # Run
-FROM mcr.microsoft.com/dotnet/core/runtime:3.0 AS run
+FROM mcr.microsoft.com/dotnet/core/runtime:3.1 AS run
 WORKDIR /app
 
 COPY --from=build /src/DiscordChatExporter.Cli/publish ./