Commands to open external resources.

[davidcanadas]

This PR introduces the following new commands to open some well-known external resources as regular Visual Studio Code panels:

• amiga.externalResources.gradientMaster opens Deadliner's The Amiga Gradient Master tool to assist you creating color gradients for Copperlists).
• amiga.externalResources.imageTool opens the Deadliner's Image Tool to assist you converting images to different Amiga formats.
• amiga.externalResources.colorReducer opens the Deadliner's Color Reducer tool to assist you reducing the number of colors in images in a smart manner.
• amiga.externalResources.bltconCheatSheet opens the Deadliner's BLTCON Cheat Sheet tool that helps you designing Blitter operations.
• amiga.externalResources.amigaHRM opens the Amiga Hardware Reference Manual TOC hosted at amigadev.elowar.com.

A new function launchUtils has been added to utils.ts in order to open any URL in a VSCode panel.

[davidcanadas]

Some functionality related to Deadliners' tools is not available in embedded mode. Will take a look into it.

Only amiga.externalResources.amigaHTM left at the moment, rest were removed.

In the future, I will provide some sort of minimal browser functionality instead of adding code to utils.ts.

[davidcanadas]

Created a minimal browser function, tested and restored all the external resources.