feat(schema): Doc for UniDirectionalOneToManyWithOneDbSet

[kilfour]

Moved File to own namespace.
Removed Property Name as it's redundant.
Removed sqlite test as there is no (apart from ddl dialect) noticable difference. Tried to put live code samples in the doc.
Fixes #24.

Generated Markdown Included Below:

Uni Directional One To Many With One Db Set

Because the entity used in the DbSet has a collection of another entity type, the latter are mapped as well.
EF infers and includes related entities in the schema even when only one side is explicitly registered in the DbContext.

When using the following simple model of one Blog containing many Posts:

public class Blog
{
    public int Id { get; set; }
}

public class Post
{
    public int Id { get; set; }
    public Blog Blog { get; set; } = default!;
}

And then adding a DbSet<Blog> to the DbContext EF generates the following ddl for Sql Server:

Blog:

    [
        "CREATE TABLE [Blog] (",
        "    [Id] int NOT NULL IDENTITY,",
        "    CONSTRAINT [PK_Blog] PRIMARY KEY ([Id])",
        ");"
    ];

Post:

    [
        "CREATE TABLE [Posts] (",
        "    [Id] int NOT NULL IDENTITY,",
        "    [BlogId] int NOT NULL,",
        "    CONSTRAINT [PK_Posts] PRIMARY KEY ([Id]),",
        "    CONSTRAINT [FK_Posts_Blog_BlogId] FOREIGN KEY ([BlogId]) REFERENCES [Blog] ([Id]) ON DELETE CASCADE",
        ");"
    ];

Index:

 "CREATE INDEX [IX_Posts_BlogId] ON [Posts] ([BlogId]);";

Note: No other mappings were added.