Not sure about active state of imageContainer

[henrych4]

First, thanks for the great library.

Here is the situation: Toolbar of ImageNode is activated when node is clicked even the editor is set to be read-only. And it is probably related to the following line: https://github.com/Canner/canner-slate-editor/blob/0330dc6000a3e31ff6aa7a46309c54eddb6c4acf/packages/renderer/renderer/src/components/imageContainer.js#L42

After taking a deeper look into the history, it seems that in the commit https://github.com/Canner/canner-slate-editor/commit/47668498c7e763f5e027f8cbc8d6557a2c29bfff, code was refactored but variable active was wrongly assigned.

Previously, toolbar is active when the condition (!isSelected || readOnly) is false, ie. active toolbar only when ImageNode is selected and is not readOnly. Therefore variable active should be set to the negation of (!isSelected || readOnly), ie.

const active = isSelected && !readOnly;