Fix #200 component save

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#200

Describe what the PR does

Option 1 in #200 (comment)

In current master to save to server the logic is already outside of the component using ref.

The suggestion is to revisit that, and move the logic for local storage saving outside of the component as an optional module available at user discretion.

This also leaves to the user(developer) the responsibility for the logic on what to do when local storage maxes out. As well as whether they'd rather use some other form of local storage, eg indexDb.

Adds the following attributes to TranscriptEditor

Attributes	Description	required	type
handleAutoSaveChanges	returns content of transcription after a change	no	Function
autoSaveFormat	specify the file format for data returned by handleAutoSaveChanges,falls back on sttJsonType. or draftjs	no	string

• fileName is no longer used as key to store and retrieve from local storage, but is still in use when exporting transcript in various formats. and it's still optional.
• logic in onChange to auto save in TimedTextEditor was trigger a bit too often, as it was not inside the check to see if the content of draftJs had changed (this.state.editorState.getCurrentContent() !== editorState.getCurrentContent()) so moved it to only be triggered if content has been modified (inserted, deleted etc..)
• updated TranscriptEditor storybook (http://localhost:6006/?path=/story/transcripteditor--default)
• setState is async so changed the logic to use result of updateTimestampsForEditorState when returning data for autoSave.
• added an auto save text area for inspection and troubleshooting in demo app in storybook next to the analytics text area
• moved function to save and retrieve from local storage in local-storage.js under the demo app, consider whether it's work, in a separate PR, showcase how local storage save would work in the demo app etc.. I'd say low priority tho?

State whether the PR is ready for review or whether it needs extra work

Ready for review

Additional context

related Issue
#176
PRs
#177
#199

Once this PR is merged it be good to

• update the the storybook on gh pages
• update npm

[emettely]

Looks good - thanks for updating the docs + demos also. If I understood correctly, the AutoSaveChanges is what gives the file extension? Not so sure if the autoSaveFormat is an option that you would want to be able to configure.
Anyways, I have one code suggestion (see below).