Readme (and consequent) edits

[c-suh]

Address Issue #5 with the following:

• Fix discrepancy between stating 'integers only' and not adhering to it in practice or example.
• Explicitly state what unit is used with the 'integers only' values.
• Simplify and explain constraints such as the closed interval for the offset configurable variable.
• Expand explanation of the additionalLinks configurable variable to match its JSON structure.
• Reorder the JSON syntax in config.js to mirror the order of explained configurable variables in the README.

Additional changes:

• Modularize JavaScript handling of configurable variables.
• Implement constraints on the offset configurable variable so that the Feedback tab is never out of the viewport.
• Add logic to better place the Feedback tab according to its width and height.
• Rename 'followupLinks' to 'additionalLinks'.