Feature/preparation for v1 release

[OlegZee]

This PR adds many more tests to cover reader and writer classes, adds missing documentation and fixes compiler warnings.

[Copilot]

Pull Request Overview

This PR prepares the library for v1 release by enriching documentation, expanding test coverage, and resolving compiler warnings.

• Added XML documentation for many core classes and methods (e.g., VInt, StreamExtensions, DTDBase, EbmlWriter, exception types).
• Introduced extensive NUnit tests for EbmlWriter covering constructors, string, binary, numeric, date/time, master elements, and unknown-size containers.
• Added null-checks, a Dispose method, and updated copyright years.

Reviewed Changes

Copilot reviewed 9 out of 10 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
Src/Core/VInt.cs	Added XML docs for implicit conversion, equality, hash, and ToString
Src/Core/StreamExtensions.cs	Documented StreamExtensions class and ReadFully method
Src/Core/MasterBlockWriter.cs	Added Dispose() method and docs
Src/Core/ElementType.cs	Documented new None enum member
Src/Core/ElementDescriptor.cs	Added overrides (GetHashCode, Equals, ToString) with docs
Src/Core/EbmlWriter.cs	Updated copyright, added docs, null-check, and warning note
Src/Core/EbmlDataFormatException.cs	Added constructors with XML docs
Src/Core/DTDBase.cs	Documented factory methods, nested descriptor classes, and StandardDtd members
Src/Core.Tests/EbmlWriterTests.cs	Added comprehensive tests for EbmlWriter

Comments suppressed due to low confidence (2)

Src/Core/EbmlDataFormatException.cs:31

• Parameter cause should be named innerException to follow .NET conventions for wrapping exceptions.

		public EbmlDataFormatException(string message, Exception cause)

Src/Core/DTDBase.cs:146

• You have consecutive <summary> tags documenting two separate fields (CRC32 and Void) on one block. Each field should have its own XML doc header to ensure the comments attach correctly.

		/// </summary>

[Copilot]

The class provides a Dispose method but does not implement IDisposable. Implement IDisposable so that consumers can use using blocks and tooling can detect disposable resources correctly.