docs explorer store

[josephfusco]

The goal here is to have a Redux store registered that maintains the state of the docs explorer and allows 3rd party code to see what's in the state and write back to the state.

The docs explorer panel uses the Redux store.

Acceptance Criteria

• test: expect hovering a valid field in the document displays a popover
• test: expect cmd + click a field in the query document to open documentation in Docs browser
• test: expect clicking the docs button opens the Docs browser
• test: expect clicking the docs button when the Docs browser is open, closes the Docs browser

Possible Public State

• explorerNavStack
• push
• pop
• reset

Related

• Add a button to the "Activity Bar Panel" #110
• https://github.com/wp-graphql/wpgraphql-ide/pull/78/files#diff-68cfdabf9fa2ce99fa19fdbe25785f2622056c22f88b1f846d3ac7ffffea0744