ADR-0004: Move/update GettingStarted.md content

[bderusha]

User Story

As a carbon aware sdk user, I want all relevant docs to exist in the /docs directory, per the standard set by ADR-0004, so I can have consistent expectations about where to go for content.

Design Goals

• Find a home for all existing GettingStarted.md content.
• Understand the difference between GettingStarted and quickstart and make it clearer (or merge if no difference).
• Markdown-lint compliant

Task List

• Moving GettingStarted.md (GS) into docs
• Review GS and quickstart.md (QS) and identify similarities/overlap in content
• Decide whether GS ans QS should be merged into a single doc or own different spheres (idea: one is architecture focused; one code focused....)
• Leverage outcome ^^ to also help guide new users on navigating other documentation

Acceptance Criteria

• GettingStarted.md no longer exists in the root directory
• User have a clear guide for starting out with the SDK
• All unique pieces of information from the original GettingStarted.md can be found somewhere in /docs
• Content touched is markdown-lint compliant

[JenMadiedo]

@Kpopovs1 taking point, with @JenMadiedo. Will circle back with @in4margaret when she returns.