Add support for vertical,horizontal grid layout.

[xsahil03x]

This pull request includes several changes to enhance the functionality of the ShimmerRecyclerView by adding support for both vertical and horizontal grid layouts. The most important changes include updating the layout XML files, modifying the ShimmerRecyclerView class to handle new layout manager types, and updating the attributes XML file.

Enhancements to ShimmerRecyclerView:

• shimmer/src/main/java/com/cooltechworks/views/shimmer/ShimmerRecyclerView.java: Added support for GRID_VERTICAL and GRID_HORIZONTAL layout manager types and updated the init method to handle these new types. [1] [2] [3]

Updates to layout XML files:

• app/src/main/res/layout/activity_grid.xml: Changed shimmer_demo_layout_manager_type from grid to grid_vertical.
• app/src/main/res/layout/activity_second_grid.xml: Changed shimmer_demo_layout_manager_type from grid to grid_vertical.

Updates to attributes XML file:

• shimmer/src/main/res/values/attrs.xml: Updated shimmer_demo_layout_manager_type to include grid_vertical and grid_horizontal enums.