Add the option to re-arrange sub-projects in the parent's show action

https://ombulabs.atlassian.net/browse/DT-247

**Branch/Commit:**

Main branch

**Describe the feature:**

When I need to re-arrange the sub-projects of a given project, I want to be able to do that from the show action of that project.

**Problem:**

Currently, the only place to re-order sub-projects is in the list of projects

**Mockups:**

The show action of a project could show the sub-projects cards listed supporting draganddrop.

**I will abide by the [code of conduct](https://github.com/fastruby/points/blob/main/CODE_OF_CONDUCT.md)**

Start with the project's show action and the existing project list, where sub-project reordering currently works. Compare how the sub-project cards are displayed and how drag-and-drop ordering is persisted there; done means the parent's show action displays reorderable sub-project cards with the same ordering behavior.

Written by the indexing model from the issue text.