Display GraphExplorer version in client UI

[nestoralvarezd]

Issue 77

Description of changes:

• Display the version number in the top bar of all workspaces.
• The version number is extracted from the package.json version number and injected into the application through the GRAPH_EXP_VERSION variable, which can be globally accessed by the application components.

[joywa]

Can we remove the "V" from this? I think it looks cleaner without. Let's also add some "Release" documentation on what exactly needs to be changed in which files when we are ready to increment the release number: https://github.com/aws/graph-explorer/blob/main/additionaldocs/development.md

[joywa]

Looks good to me. Adding @michaelnchin for one more review. Let's merge this last, when we're ready to release.

[michaelnchin]

All LGTM, thanks!