Add `Branches` section.

[HarshKapadia2]

• Add Branches section to the General # 2 section, after the Internal Working of Git sub-section.
• Use Gaurav Sen's Git video and this git for some commands

[HarshKapadia2]

• A visualization resource for branches. (Can be added to the resources section as well.)

[HarshKapadia2]

• [ ] Branch hierarchy
  • Point no. 6 of this Medium article
  • Effect of hierarchy to ./.git/refs/heads in 2nd para of this StackOverflow answer

[HarshKapadia2]

• [ ] Branch renaming
• [ ] Default branches
  • What are they?
  • The whole master vs main issue as explained in issue #47.
  • Reference branch renaming