Turbo Render (#298)

* More responsive React updates on scroll

* `Icon`s now use shadow dom

* Faster Sparkline

* Recycle table rows

* Separate Header from Chain to avoid vdom diffing

* Separate THead from Row.HEADER to avoid vdom diffing

* Throttle rendering updates on chain tabs, also styles

* Minor tweaks and fixes

* Created components for all columns

* Wrapping up Column refactor

* Rename Row--td to Column

* Lazy `Ago`

* Update styles for faster layouting

* Minor cleanup

* Fix Connection

* Use shadow DOM in `PolkadotIcon`

* Comments and tweaks for the List component

* Faster Tooltip and Truncate

* Minor tweaks

* Tooltiped columns can now be copied

* Future-proof Connection

* Remove the <div> wrapper from Icon

* Fix dash on missing graph data

* Clean up some SVGs

* Cleanup and comments

* Localize the use of `previousKeys` to `recalculateKeys`

* Custom appState disjoint from React component state

* Make appState and appUpdate refs readonly

* Cleanup

frontend/src/utils.ts

@@ -95,3 +95,19 @@ export function setHashData(val: HashData) {
 
   window.location.hash = `#${tab}/${encodeURIComponent(chain)}`;
 }
+
+let root: null | SVGSVGElement = null;
+export const W3SVG = 'http://www.w3.org/2000/svg';
+
+// Get a root node where we all SVG symbols can be stored
+// see: Icon.tsx
+export function getSVGShadowRoot(): SVGSVGElement {
+  if (!root) {
+    root = document.createElementNS(W3SVG, 'svg');
+    root.setAttribute('style', 'display: none;');
+
+    document.body.appendChild(root);
+  }
+
+  return root;
+}