feat(window): create Window & WindowSpec

[sjrusso8]

Description

feat(window): create Window & WindowSpec

• create two new structs for Window & WindowSpec based a similar implementation of the existing Spark API.
• add unit tests for coverage of specific Window methods
• add new over method onto Column and add unit test
• update Rust Docs and README for `Window

Example Usage

let df = spark.createDataFrame(&data)?;

let window = Window::new()
    .partitionBy(col("category"))
    .orderBy([col("id")])
    .rowsBetween(Window::currentRow(), 1);

let df = df
    .withColumn("sum", sum("id").over(window))
    .sort([col("id"), col("category"), col("sum")]);