Remove pug in favor of a few posthtml plugins

Pug caused no end of issues and is frankly far too heavy-weight for
what I want.

As it turns out, there are posthtml plugins to do everything pug did
for me, so it's getting kicked out.

.posthtmlrc

@@ -0,0 +1,36 @@
+{
+  "plugins": {
+    "posthtml-md": {
+      "root": "src",
+    },
+    "posthtml-extend": {
+      "root": "src",
+    },
+    "posthtml-include": {
+      "root": "src",
+    },
+    "posthtml-favicons": {
+      "root": "src",
+      "outDir": "./dist/browser/",
+      "configuration": {
+        "appName": "tlater.net",
+        "appShortName": "tlater.net",
+        "appDescription": "tlater's home page",
+        "developerName": "Tristan Daniël Maat",
+        "developerURL": "https://tlater.net",
+        "dir": "auto",
+        "lang": "en-US",
+        "background": "#0f0f0f",
+        "theme_color": "#991dce",
+        "appleStatusBarStyle": "black-translucent",
+        "display": "browser",
+        "orientation": "any",
+        "start_url": "https://tlater.net",
+        "version": "1.0",
+        "icons": {
+          "favicons": true,
+        },
+      },
+    },
+  },
+}