Copy knob state URL looses value type

[Silic0nS0ldier]

Describe the bug
The knobs addon supports copying a URL with existing knob states. Some knobs may use a number as the value, however they are casted to a string when restoring knob state using the copied URL.

To Reproduce
https://github.com/Silic0nS0ldier/storybook-knobs-copy-bug

System

System:
  OS: macOS 10.15.7
  CPU: (16) x64 Intel(R) Core(TM) i9-9980HK CPU @ 2.40GHz
Binaries:
  Node: 12.22.1 - /usr/local/opt/node@12/bin/node
  Yarn: 1.22.10 - /usr/local/bin/yarn
  npm: 6.14.12 - /usr/local/opt/node@12/bin/npm
Browsers:
  Chrome: 90.0.4430.85
  Edge: 90.0.818.49
  Safari: 14.1
npmPackages:
  @storybook/addon-a11y: ^6.1.21 => 6.1.21 
  @storybook/addon-actions: ^6.1.21 => 6.1.21 
  @storybook/addon-knobs: ^6.1.21 => 6.1.21 
  @storybook/addon-viewport: ^6.1.21 => 6.1.21 
  @storybook/addons: ^6.1.21 => 6.1.21 
  @storybook/react: ^6.1.21 => 6.1.21

Additional context
NA

[shilman]

FYI, we’ve released addon-controls in Storybook 6.0. Controls are portable, auto-generated knobs that are intended to replace addon-knobs, which are slated for deprecation.

• Controls documentation
• Migration instructions

Please upgrade and try out controls today!

[Silic0nS0ldier]

Appreciate the heads up. addon-controls and addon-knobs presumably play together fine right? (for context, there are 1110 and growing stories using @storybook/addon-knobs in the repo where this issue was identified, making incremental adoption a must)

[shilman]

@Silic0nS0ldier Yes, they can exist side by side, possibly even in the same story/component. But I'd probably convert them file by file, i.e. when you touch a component's stories, convert them all into controls in one shot.

[mctrafik]

I'll take a stab at fixing this.