Improve "Making Plugins" documentation

**Your Godot version:** 3.4

**Issue description:**
Making plugins documentation is a bit confusing in some parts and has inconsistencies between the two examples.

Confusing:
- End of the first example links to the bottom of the page to check the results. That explains how to check the results of the dock, to me it made it seem like the button example will show up in a dock, not a node resource. I think this would greatly benefit with more instructions and pictures on how to check the button example.

Inconsistencies:
1. Methods for initially creating plugins are different
- Button example uses Godot dialog to create plugin files
- Custom Dock example manually creates the files (Not easily done in the Godot file explorer)

2. Values for creating plugins are different:
- Button
```
Plugin Name: My Custom Node
Subfolder: my_custom_node
Description: A custom node made to extend the Godot Engine.
Author: Your Name Here
Version: 1.0.0
Language: GDScript
Script Name: custom_node.gd
Activate now: No
```
- Dock (with [plugin] header)
```
name="My Custom Dock"
description="A custom dock made so I can learn how to make plugins."
author="Your Name Here"
version="1.0"
script="custom_dock.gd"
```

Some of these confusions could just be me and they're not a huge deal, but I think it'd be helpful to clarify some of these things.

**URL to the documentation page (if already existing):**
https://docs.godotengine.org/en/stable/tutorials/plugins/editor/making_plugins.html

https://github.com/godotengine/godot-docs/blob/master/tutorials/plugins/editor/making_plugins.rst