Add app build script for Linux

app/build.sh

@@ -0,0 +1,25 @@
+#!/bin/bash
+set -e
+
+if [ ! -f "DiscordHistoryTracker.sln" ]; then
+	echo "Missing DiscordHistoryTracker.sln in working directory!"
+	exit 1
+fi
+
+makezip() {
+	pushd "./bin/$1"
+	zip -9 -r "../$1.zip" .
+	popd
+}
+
+rm -rf "./bin"
+
+configurations=(win-x64 linux-x64 osx-x64)
+
+for cfg in ${configurations[@]}; do
+	dotnet publish Desktop -c Release -r "$cfg" -o "./bin/$cfg" -p:PublishSingleFile=true -p:IncludeNativeLibrariesForSelfExtract=true -p:PublishReadyToRun=false -p:PublishTrimmed=true --self-contained true
+	makezip "$cfg"
+done
+
+dotnet publish Desktop -c Release -o "./bin/portable" --self-contained false
+makezip "portable"

app/global.json

@@ -0,0 +1,6 @@
+{
+    "sdk": {
+        "version": "5.0.0",
+        "rollForward": "latestMinor"
+    }
+}