Upgrade architecture + 5.0 Bot API (#469)

Upgrade architecture + 5.0 Bot API (#469)
* Moved `methods`, `types` and `client` to root package
* Removed update handler from routers to dispatcher
* Reworked events propagation mechanism to handlers
* Reworked inner middlewares logic (very small change)
* Updated to Bot API 5.0
* Initial migration from MkDocs to Sphinx + config for readthedocs

docs2/_static/stylesheets/extra.css

@@ -0,0 +1,22 @@
+@font-face {
+    font-family: 'JetBrainsMono';
+    src: url('https://cdn.jsdelivr.net/gh/JetBrains/JetBrainsMono/web/woff2/JetBrainsMono-Regular.woff2') format('woff2'),
+    url('https://cdn.jsdelivr.net/gh/JetBrains/JetBrainsMono/web/woff/JetBrainsMono-Regular.woff') format('woff'),
+    url('https://cdn.jsdelivr.net/gh/JetBrains/JetBrainsMono/ttf/JetBrainsMono-Regular.ttf') format('truetype');
+    font-weight: 400;
+    font-style: normal;
+}
+
+code, kbd, pre {
+    font-family: "JetBrainsMono", "Roboto Mono", "Courier New", Courier, monospace;
+}
+
+.highlight * {
+    background: #f0f0f0;
+}
+
+@media (prefers-color-scheme: dark) {
+    .highlight * {
+        background: #424242;
+    }
+}