Add token management to Settings

- Tracked Tokens well in settings with [x] remove buttons
- New settings-addtoken view with:
  - Top-10 quick-pick buttons (tracked ones dimmed+disabled)
  - Top-100 dropdown showing "Token Name (SYMBOL)", tracked disabled
  - Manual contract address entry with RPC lookup
- View comment in helpers.js about keeping README in sync

src/popup/views/helpers.js

@@ -8,6 +8,8 @@ const {
 } = require("../../shared/prices");
 const { state, saveState } = require("../../shared/state");
 
+// When views are added, removed, or transitions between them change,
+// update the view-navigation documentation in README.md to match.
 const VIEWS = [
     "welcome",
     "add-wallet",
@@ -23,6 +25,7 @@ const VIEWS = [
     "receive",
     "add-token",
     "settings",
+    "settings-addtoken",
     "transaction",
     "approve-site",
     "approve-tx",