Adding handy Powershell script to apply the mod on Windows

darkslack.ps1

@@ -0,0 +1,80 @@
+$slackBaseDir = "$env:HOMEPATH\AppData\Local\slack\"
+$installations = Get-ChildItem $slackBaseDir -Directory | Where-Object { $_.Name.StartsWith("app-") }
+$version = $installations | Sort-Object { [version]$_.Name.Substring(4) } | Select-Object -Last 1
+Write-Output "Choosing highest present Slack version: $version"
+
+$customContent = @'
+// First make sure the wrapper app is loaded
+document.addEventListener("DOMContentLoaded", function() {
+
+   // Then get its webviews
+   let webviews = document.querySelectorAll(".TeamView webview");
+
+   // Fetch our CSS in parallel ahead of time
+   const cssPath = 'https://cdn.rawgit.com/widget-/slack-black-theme/master/custom.css';
+   let cssPromise = fetch(cssPath).then(response => response.text());
+
+   let customCustomCSS = `
+   :root {
+      /* Modify these to change your theme colors: */
+      --primary: #09F;
+      --text: #CCC;
+      --background: #080808;
+      --background-elevated: #222;
+   }
+   div.c-message.c-message--light.c-message--hover
+	{
+	color: #fff !important;
+	background-color: #222 !important;
+	}
+
+	span.c-message__body,
+	a.c-message__sender_link,
+	span.c-message_attachment__media_trigger.c-message_attachment__media_trigger--caption,
+	div.p-message_pane__foreword__description span
+	{
+			color: #afafaf !important;
+	}
+
+	pre.special_formatting{
+		background-color: #222 !important;
+		color: #8f8f8f !important;
+		border: solid;
+		border-width: 1 px !important;
+
+	}
+   `
+
+   // Insert a style tag into the wrapper view
+   cssPromise.then(css => {
+      let s = document.createElement('style');
+      s.type = 'text/css';
+      s.innerHTML = css + customCustomCSS;
+      document.head.appendChild(s);
+   });
+
+   // Wait for each webview to load
+   webviews.forEach(webview => {
+      webview.addEventListener('ipc-message', message => {
+         if (message.channel == 'didFinishLoading')
+            // Finally add the CSS into the webview
+            cssPromise.then(css => {
+               let script = `
+                     let s = document.createElement('style');
+                     s.type = 'text/css';
+                     s.id = 'slack-custom-css';
+                     s.innerHTML = \`${css + customCustomCSS}\`;
+                     document.head.appendChild(s);
+                     `
+               webview.executeJavaScript(script);
+            })
+      });
+   });
+});
+'@
+
+Add-Content "$($version.FullName)\resources\app.asar.unpacked\src\static\index.js" $customContent
+Add-Content "$($version.FullName)\resources\app.asar.unpacked\src\static\ssb-interop.js" $customContent
+
+Write-Output "Mod done - please restart Slack"
+Read-Host