Add existing virtual relation strategies to the README

[suzuki]

About

I found undocumented strategies: identical, identicalSingularTableName

tbls/config/naming.go

Lines 24 to 49 in 76d30f8

	func SelectNamingStrategy(name string) (*NamingStrategy, error) {
	switch name {
	case "", "default":
	// default
	return &NamingStrategy{
	ParentTable: defaultParentTableNamer,
	ParentColumn: defaultParentColumnNamer,
	}, nil
	case "singularTableName":
	return &NamingStrategy{
	ParentTable: singularTableParentTableNamer,
	ParentColumn: singularTableParentColumnNamer,
	}, nil
	case "identical":
	return &NamingStrategy{
	ParentTable: defaultParentTableNamer,
	ParentColumn: identicalParentColumnNamer,
	}, nil
	case "identicalSingularTableName":
	return &NamingStrategy{
	ParentTable: singularTableParentTableNamer,
	ParentColumn: identicalParentColumnNamer,
	}, nil

I just wanted to use an identiacal strategy.

[k1LoW]

@suzuki Thank you!!!