Add 'get' canvas functions to ranges

[MImranAsghar]

• Add getCanvases, getCanvasById, getCanvasByIndex functions for the range type

[stephenwf]

I'm not sure why, but 3 tests appear to be failing now:

195 passing (2s)
  3 failing
  1) pres3 presentation 3 range has a canvas:
     TypeError: Cannot read property '__jsonld' of undefined
      at context.<anonymous> (test/tests/pres3.js:48:96)
  2) pres3 presentation 3 has an annotation body:
     TypeError: Cannot read property 'getContent' of undefined
      at context.<anonymous> (test/tests/pres3.js:54:26)
  3) pres3 presentation 3 has a label:
     TypeError: Cannot read property 'getLabel' of undefined
      at context.<anonymous> (test/tests/pres3.js:62:26)

[MImranAsghar]

Ah interesting, looking into it 👍

[MImranAsghar]

Hi @stephenwf , fixed the tests

[MImranAsghar]

Hi @stephenwf , I was wondering if you got a chance to take a look at the changes. do you think this can be merged? 🤔

[stephenwf]

Sorry yes I think so 👍 @edsilv ?

[marlo-longley]

Hello Manifesto team, we are auditing some older issues and wondering if this is still a candidate to be merged.
For example we are hoping to use it here: ProjectMirador/mirador#2949
Thank you for taking a look!

[demiankatz]

Thanks for checking in, @marlo-longley. I haven't previously reviewed this one (at the time this was going on, I wasn't as active in this project), but I'm certainly open to giving it a closer look. It seems that there are some conflicts that need to be resolved, though, so the first question is how we get this in shape to be mergeable. Is @MImranAsghar still actively engaged with this? If not, should we close this PR and open a fresh one that somebody is able to maintain?

[marlo-longley]

@demiankatz thanks! Yes, I rebased this branch and put up a new PR here #181

[demiankatz]

Great, I'll close this PR so we can focus on the new one. Thanks, @marlo-longley!