Modified the Semantic Analyser for DogLang Compiler..

[AvanishSalunke]

Introduced a semantic analysis phase and fixes several underlying bugs to improve the stability and correctness of the DogLang compiler.

Changes done :

• Implemented the Semantic Analyzer: A new SemanticAnalyser class was created to check the code for logical errors after it is parsed but before it is run by the interpreter.
• Added Undeclared Variable Checks: The analyser now detects when a variable is used before it has been assigned a value and reports a SemanticError, preventing crashes during runtime.
• Introduced Type Checking for Conditions: It now validates the conditions inside sniff and wagtail statements to ensure they are boolean comparisons (e.g., a < 10), rejecting incorrect types.
• Fixed Critical SymbolTable Bug: The SymbolTable was refactored to remove a major bug where it used a global state. It is now instance-based, making the language more stable and predictable.
• Integrated into the Compiler Pipeline: The Interpreter's flow was updated to include this new analysis step, creating a proper Tokenize -> Parse -> Analyze -> Interpret sequence and establishing a custom SemanticError for clear error messages.

Fixes #2

Kindly go through the changes , I would like to contribute more on this...
Thankyou!

[AvanishSalunke]

@Pallavrai resolved the conflicts that arised do the changes done in the main branch.
Kindly do through the changes..
Thankyou!!