feat: add support for excluding SQL files from directory loading

[DevD4v3]

Motivation

While integrating YeSql into my CTF project, I needed to keep a schema.sql file alongside the query files.

The schema script is executed only once during application startup to create the database schema, but LoadFromDirectories() also loaded it into the ISqlCollection, where it served no purpose.

This change introduces an opt-in configuration method that allows specific SQL files to be excluded from directory loading without changing the existing directory structure.

Changes

• Add YeSqlLoader.Exclude() to exclude SQL files from LoadFromDirectories().
• Normalize file paths to file names before storing exclusions.
• Store excluded file names in a HashSet<string> to prevent duplicates and provide efficient lookups.
• Add XML documentation.
• Add unit tests covering the new behavior.
• Update the sample project.

Usage

ISqlCollection sqlStatements = new YeSqlLoader()
    .Exclude("client.sql", "employee.sql")
    .LoadFromDirectories("yesql");

Console.WriteLine(sqlStatements.TryGetStatement("GetClients", out var sql)
    ? sql
    : "'GetClients' is unavailable because it belongs to an excluded SQL file.");

Console.WriteLine(sqlStatements.TryGetStatement("GetEmployees", out sql)
    ? sql
    : "'GetEmployees' is unavailable because it belongs to an excluded SQL file.");