Update README.md

[iscordian]

This pull request enhances the project's README file with several improvements aimed at increasing clarity, completeness, and user-friendliness. These changes make it easier for users to get started with PojavLauncher, understand its capabilities, and contribute to the project.

Key Changes:

• Table of Contents Added: A table of contents has been added to the top of the README for easier navigation to different sections.
• Simplified Build Instructions: The build instructions have been reorganized and simplified, especially the "Quick Build" section, to make it easier for new users to build the project. The detailed instructions are still available for advanced users. Clarified the use of pre-built JREs from CI.
• Known Issues Section Improved: The "Known Issues" section now links directly to the project's issue tracker on GitHub, providing a more structured and up-to-date view of known issues.
• FAQ Section Added: A placeholder FAQ section has been added to address common user queries. This section can be populated with actual FAQs in subsequent updates. A link to the wiki has been added as well.
• Contributing Guidelines Enhanced: While contributions were already welcomed, this PR adds a placeholder CONTRIBUTING.md file and encourages users to follow contribution guidelines (which should be added later).
• Support Section Added: A "Support" section has been added, directing users to the project's Discord server for assistance.
• Roadmap Section Added: A "Roadmap" section has been created to outline current focus, future plans, and encourage community feedback. This provides transparency and helps potential contributors understand the project's direction.
• Credits and Dependencies Completed: The list of credits and dependencies has been finalized to ensure proper attribution and license compliance.
• General Formatting and Clarity: Minor formatting and wording improvements have been made throughout the README to enhance readability.

Benefits:

• Improved Onboarding: New users will find it easier to understand PojavLauncher and get it running.
• Increased Community Engagement: Clearer contribution guidelines and a roadmap will encourage community involvement.
• Better Support: A dedicated support section will streamline user assistance.
• Enhanced Transparency: The roadmap and complete credits section provide greater transparency about the project's direction and dependencies.

Testing:

No code changes were made in this PR, only documentation updates. Therefore, no specific testing is required. However, a visual review of the rendered README on GitHub is recommended to ensure proper formatting.