Add runtime MIME helpers and automated data sync

[KSemenenko]

Summary

• add runtime registration and reverse lookup APIs to MimeHelper, improve extension handling, and expand MIME categorisation
• extend content-based detection with richer signatures and short-stream handling, and cover the changes with new unit tests
• add a data sync console utility, refresh mimeTypes.json, and update the documentation with the new features
• add scheduled GitHub Action automation and multi-source sync support for the MIME database

Testing

• dotnet test (fails in CI container: dotnet command not available)

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https://chatgpt.com/codex/tasks/task_e_68ea08250b3483269ee0369c9166f2aa

[Copilot]

Pull Request Overview

This PR adds comprehensive runtime MIME helpers and automated data sync capabilities to the MimeTypes library. It enhances the existing MIME type detection with content-based analysis, reverse lookup functionality, and runtime registration APIs, while introducing automated tooling to keep the MIME database current with upstream sources.

• Adds runtime registration/unregistration APIs and reverse lookup functionality to MimeHelper
• Implements content-based MIME detection with rich file signature analysis and improved categorization
• Introduces a data sync console utility with multi-source support and scheduled GitHub Actions automation

Reviewed Changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
README.md	Complete documentation rewrite showcasing new features with examples
ManagedCode.MimeTypes/mimeTypes.json	Updated MIME database with 100+ new entries and compound extensions
ManagedCode.MimeTypes/MimeTypeCategory.cs	Added Script, Binary, Multipart, and Message categories
ManagedCode.MimeTypes/MimeHelper.cs	Major expansion with runtime APIs, content detection, and thread-safe lookups
ManagedCode.MimeTypes/ManagedCode.MimeTypes.csproj	Updated LangVersion to preview
ManagedCode.MimeTypes.sln	Added sync utility project reference
ManagedCode.MimeTypes.Tests/	New comprehensive test coverage for all features
ManagedCode.MimeTypes.Sync/	New console utility for automated MIME database synchronization
ManagedCode.MimeTypes.Generator/MimeTypeSourceGenerator.cs	Enhanced generator with proper escaping and registration calls
.github/workflows/mime-sync.yml	Automated weekly sync workflow

Comments suppressed due to low confidence (2)

ManagedCode.MimeTypes/MimeHelper.cs:1

• This change from 'application/javascript' to 'text/javascript' for .mjs files may break existing applications that expect the application MIME type. Consider if this is an intentional breaking change or if backward compatibility should be maintained.

using System;

ManagedCode.MimeTypes/MimeHelper.cs:1

• [nitpick] The x_b and x_t entries have been moved to the end of the JSON file, which changes their ordering. Ensure this reordering doesn't affect any order-dependent logic or tests.

using System;

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[Copilot]

Creating a new char array for each line split is inefficient. Consider using a static readonly char array or string.Split overload that takes individual char parameters.

[coveralls]

Pull Request Test Coverage Report for Build 18430034647

Details

• 354 of 471 (75.16%) changed or added relevant lines in 2 files are covered.
• 154 unchanged lines in 3 files lost coverage.
• Overall coverage increased (+4.9%) to 53.977%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
ManagedCode.MimeTypes.Generator/MimeTypeSourceGenerator.cs	0	11	0.0%
ManagedCode.MimeTypes/MimeHelper.cs	354	460	76.96%

Files with Coverage Reduction	New Missed Lines	%
ManagedCode.MimeTypes.Generator/MimeTypeSourceGenerator.cs	1	0.0%
ManagedCode.MimeTypes/MimeHelper.cs	2	74.81%
ManagedCode.MimeTypes/obj/Generated/ManagedCode.MimeTypes.Generator/ManagedCode.MimeTypes.Generator.MimeTypeSourceGenerator/MimeHelper.Properties.cs	151	50.28%

Totals
Change from base Build 16629812820:	4.9%
Covered Lines:	1659
Relevant Lines:	3125

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💛 - Coveralls