Add emoji support

[HarshKapadia2]

• :hammer: should render 🔨 in the web app.
• Ensure that existing emoji support doesn't change.
• This change will have to be made when the commit message has been read, so before returning from getCommitMsg() in generateObjects.js.
  • One way to implement this would be to check for the indices of all the colons (:) and then try to extract the text between two colons to check if it matches an emoji text.

Current behaviour:

Expected behaviour:

• :sparkles: should render as ✨ in the commit message.
• :truck: should render as 🚚 in the commit message.

Originally posted by @HarshKapadia2 in #40 (comment)