Rename GuitarDiagramsJS.addCanvas() method

[KCarlile]

Background

The GuitarDiagramsJS class has a public method called addCanvas(paramParentElementID) that is used for adding the new HTML5 canvas element to a parent element for drawing the diagram. The name of this method is not clear in terms of what it does or how it should be used.

Acceptance Criteria

• [x] GuitarDiagramsJS.addCanvas(paramParentElementID) is renamed to something that more clearly states the purpose
• [x] Any documentation is updated to reflect the name change

Approach

• TBD

Notes

TBD

[KCarlile]

PR into develop: #51. PR into `10-productize-documentation: #52.