Added command line input functionality

[rohanahuja4]

Description:
This pull request introduces the addition of command line input functionality.

1. Command Line Input:

   • Added a new function, dpll(cnf_argument), to solve a single CNF formula when called from the command line.
   • The function accepts a CNF formula as an argument preceded by a “solve” argument (e.g., python3 SATSolver.py solve [formula] allowing users to input formulas directly in the command line.
   • The input format slightly modifies the original CNF syntax, where variables are represented by uppercase letters and negation is denoted by the tilde (~) symbol. This is to avoid a misinterpretation of “!” as a special character.

2. Error Handling:

   • Implemented input validation to ensure that the CNF formula provided via the command line is in the correct format.
   • If the input format is invalid, an error message is displayed, guiding the user to submit a valid CNF formula.

These updates improve the usability of the SAT Solver, enabling users to solve individual CNF formulas conveniently from the command line. The error handling ensures that only valid formulas are processed.