Add key binding listener and default config

Fix #2278

Author: jhildenbiddle

src/core/config.js

@@ -21,6 +21,26 @@ export default function (vm) {
       formatUpdated: '',
       ga: '',
       homepage: 'README.md',
+      keyBindings: {
+        // Focus on main content
+        'alt+c': e => {
+          const containerElm = document.querySelector('.markdown-section');
+          const focusElm = containerElm.querySelector(
+            'button, [href], input, select, textarea, [tabindex]:not([tabindex="-1"])'
+          );
+
+          focusElm && focusElm.focus();
+        },
+        // Toggle sidebar menu
+        'alt+t': e => {
+          const toggleElm = document.querySelector('.sidebar-toggle');
+
+          if (toggleElm) {
+            toggleElm.click();
+            toggleElm.focus();
+          }
+        },
+      },
       loadNavbar: null,
       loadSidebar: null,
       maxLevel: 6,

src/core/event/index.js

@@ -43,6 +43,29 @@ export function Events(Base) {
       } else {
         body.classList.add('sticky');
       }
+      // Bind keyboard shortcuts
+      on('keydown', e => {
+        const modifiers = ['alt', 'ctrl', 'meta', 'shift'];
+
+        Object.entries(this.config.keyBindings || {}).forEach(
+          ([keyBinding, fn]) => {
+            const keys = keyBinding.split('+').map(k => k.toLowerCase().trim());
+            const isMatch = keys.every(
+              k =>
+                (modifiers.includes(k) && e[k + 'Key']) ||
+                e.key === k || // Ex: " ", "a"
+                e.code.toLowerCase() === k || // "space"
+                e.code.toLowerCase() === `key${k}` || // "keya"
+                e.keyCode === Number(k) // 32 (space), 65 (a)
+            );
+
+            if (isMatch) {
+              e.preventDefault();
+              fn(e);
+            }
+          }
+        );
+      });
     }
 
     /** @readonly */