Asking to add some string basic interview quetions for builiding confidence

[Abhirajtiwari1]

Description of Change

• Description Of change: proposing for adding a string interview quetions and a readme file listing a documentation of strings and a associated stl.
• File names: folder name: interviewquetions
• path- C-Plus-Plus\strings\interviewQuetions
  I acknowledge that all my contributions will be made under the project's license.

this pull request address thih issue: #2828

[Abhirajtiwari1]

@realstealthninja