First pre-release version of v5.0.0, published to NPM with the next tag.

This release contains all the breaking changes described in the 5.0 wiki page.

• #2564 TimezonePicker performance optimization significantly reduces time to compute timezone items.

• #2585 Added new icons: globe-network, tree, snowflake

• fix TS compiler issue in IHotkeysTarget with latest @types/react@16.3

  lerna ERR! ERROR in [at-loader] ../../node_modules/@blueprintjs/core/dist/esm/components/hotkeys/hotkeysTarget.d.ts:4:18
  lerna ERR!     TS2320: Interface 'IHotkeysTarget' cannot simultaneously extend types 'Component<any, any, any>' and 'ComponentLifecycle<any, any, never>

• new Example frame! #2489
  • Example component is now composed in render() instead of extend BaseExample
  • examples are clearly separated from surrounding text with structure for example/options/source
  • completely rewrite CSS examples so they're more similar to React examples, with checkboxes for each modifier
  • deprecate BaseExample; will remove in next beta release
• upgrade Documentalist, fix React key warnings #2510

• 📦 move react-transition-group from peer to standard dependency #2511
• 📦 new 3.0 upgrade script, improve 2.0 upgrade script #2488
• new icons: crown and tree-diagram #2507
• fix typings of HTML Table component #2509
• fix upgrade script's treatment of removed props #2486
• Button fix button width with large CSS icon only #2497
• Tabs fix vertical style #2495
• Tag improve outline behavior #2428
• Spinner adjust stroke width #2491
• Switch fix align-right style #2494
• Toaster.create() throws error if used within lifecycle method #2522
• ensureElement utility supports React.Fragment #2499

• new icons: crown, shield, tree-diagram (#2519, #2448)
• Toaster.create() throws an error if ReactDOM.render() returns null (#2523)
  • React 16 has a breaking change where ReactDOM.render() returns null if invoked within a lifecycle method, which breaks the Toaster.create() contract of returning a Toaster instance
  • we handle this by throwing an error, forcing you to refactor your usage of the Toaster to either an element ref or a singleton module

• #2413 Fix EditableText CSS classes.

• ⭐️ #2394 Add a new lint rule blueprint-classes-constants to enforce use of Classes.* constants instead of "pt-prefixed-strings". This rule is enabled by default.
  • Also added blueprint-icon-components rule to enforce JSX component or string literal usage for icon props. This rule is disabled by default and has little practical purpose until we ship individual components for the icons #2193
• removed file-header configuration as it mentioned Palantir

• ⭐️ #2325 Support for customizing the CSS class namespace pt-
  • in the upcoming 3.0 release, we will change this namespace to bp3- to avoid style conflicts with previous versions of Blueprint on the same page
  • added a new docs page about Classes to encourage use of the forward-compatible Classes constants
• #2390 Fix hot reload support ( 🎩 @dan-katz)
• #2118 Fix scroll syncing when widths/heights change ( 🎩 @mcintyret)