Add README.md for SharpCoreDB project

[Copilot]

Project was missing documentation. Added comprehensive README covering usage and capabilities.

Contents

• Features overview: SQL support, AES-256-GCM encryption, WAL, user auth, B-tree indexing
• Usage examples: DI setup, table creation, CRUD operations, JOINs, readonly mode
• Data types reference: INTEGER, TEXT, REAL, BLOB, BOOLEAN, DATETIME, LONG, DECIMAL, ULID, GUID

Quick Start

varservices=newServiceCollection();services.AddSharpCoreDB();varfactory=services.BuildServiceProvider().GetRequiredService<DatabaseFactory>();vardb=factory.Create("/path/to/db","masterPassword");db.ExecuteSQL("CREATE TABLE users (id INTEGER PRIMARY KEY, name TEXT)");db.ExecuteSQL("INSERT INTO users VALUES ('1', 'Alice')");db.ExecuteSQL("SELECT * FROM users");

Original prompt

Create the readme file for this project

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