Add JSpecify to Code Analysis (#1291)

Add JSpecify to the list of static analysis tools

Add JSpecify to the README, highlighting its role in providing
standardized nullness annotations. JSpecify aims to create a unified
framework for null-safety that works uniformly across various Java
IDEs, compilers, and static analysis tools.

This addition serves as a valuable resource for developers looking
to implement robust, tool-agnostic null checking in modern Java projects.

Author: rajneeshpatel

README.md

@@ -218,6 +218,7 @@ _Tools that provide metrics and quality measurements._
 - [Error Prone Support](https://github.com/PicnicSupermarket/error-prone-support) - Error Prone extensions: extra bug checkers and a large battery of Refaster templates.
 - [Infer](https://github.com/facebook/infer) - Modern static analysis tool for verifying the correctness of code.
 - [jQAssistant](https://jqassistant.org) - Static code analysis with Neo4J-based query language. (GPL-3.0-only)
+- [JSpecify](https://jspecify.dev/) - Standardized nullness annotations designed to work uniformly across various Java IDEs, compilers, and static analysis tools.
 - [NullAway](https://github.com/uber/NullAway) - Eliminates NullPointerExceptions with low build-time overhead.
 - [PMD](https://github.com/pmd/pmd) - Source code analysis for finding bad coding practices.
 - [p3c](https://github.com/alibaba/p3c) - Provides Alibaba's coding guidelines for PMD, IDEA and Eclipse.