Update Dockerfile to .NET 9 (#457)

Dockerfile

@@ -1,14 +1,14 @@
 ARG GIT_SHA=v0.1
 
-FROM mcr.microsoft.com/dotnet/sdk:8.0-alpine AS build
+FROM mcr.microsoft.com/dotnet/sdk:9.0-alpine AS build
 WORKDIR /src
 COPY . .
 RUN dotnet restore
 RUN dotnet publish Obsidian.ConsoleApp/ -c Release -r linux-musl-x64 --self-contained -p:PublishSingleFile=true -p:PublishReadyToRun=true -p:EnableCompressionInSingleFile=true -p:DebugType=embedded /p:SourceRevisionId=$GIT_SHA
 
 FROM alpine:latest
 WORKDIR /app
-COPY --from=build /src/Obsidian.ConsoleApp/bin/Release/net8.0/linux-musl-x64/publish/ .
+COPY --from=build /src/Obsidian.ConsoleApp/bin/Release/net9.0/linux-musl-x64/publish/ .
 RUN apk upgrade --update-cache --available && apk add openssl libstdc++ && rm -rf /var/cache/apk/*
 
 WORKDIR /files