[Docs] Added custom style to the main doc page.

Component lists are now displayed in a grid format, each accompained by
an icon.

docs/source/_static/scripts/custom.js

@@ -0,0 +1,48 @@
+document.addEventListener("DOMContentLoaded", function() {
+  const processList = (list, level, addTitle) => {
+    const title = list.parentElement.querySelector('a')
+    list.classList.add('grid')
+    if (addTitle)
+      title.classList.add('grid-title')
+
+    list.querySelectorAll(`li.toctree-l${level}`).forEach((item) => {
+      const link = item.querySelector('a')
+      if (link) {
+        item.style.cursor = 'pointer'
+        item.addEventListener('click', () => link.click())
+      }
+
+      const name = item.querySelector('a').innerText
+      const img = document.createElement('img')
+      img.src = `https://static.platypush.tech/icons/${name.toLowerCase()}-64.png`
+      img.alt = ' '
+      item.prepend(img)
+    })
+  }
+
+  const tocWrappers = document.querySelectorAll('.toctree-wrapper.compound')
+
+  if (!tocWrappers.length) {
+    return
+  }
+
+  if (window.location.pathname.endsWith('/index.html')) {
+    if (tocWrappers.length < 2) {
+      return
+    }
+
+    const referenceLists = [
+      ...tocWrappers[1].querySelectorAll('ul li.toctree-l1 ul')
+    ].slice(0, 4)
+
+    referenceLists.forEach((list) => processList(list, 2, true))
+  } else if (window.location.pathname.endsWith('/plugins.html') || window.location.pathname.endsWith('/backends.html')) {
+    if (tocWrappers.length < 1) {
+      return
+    }
+
+    const list = tocWrappers[0].querySelector('ul')
+    if (list)
+      processList(list, 1, false)
+  }
+})