Added invalid precondition syntax checker

[PraneethS42]

Proposed Changes

This pull request works on #1294. Creates a custom checker called invalid_precondition_syntax_checker.py that alerts the user if a function docstring contains invalid syntax within one of its preconditions. This currently only supports single-line preconditions, and leverages the preexisting parse_assertions method from python-ta/contracts/__init__.py.

Adds an example file and appropriate changes in documentation, as well as tests.
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Type	Applies?
🚨 Breaking change (fix or feature that would cause existing functionality to change)
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[coveralls]

Pull Request Test Coverage Report for Build 21931750535

Details

• 21 of 21 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.1%) to 89.958%

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Totals
Change from base Build 21888778658:	0.1%
Covered Lines:	3440
Relevant Lines:	3824

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💛 - Coveralls