Migs647/spm how to

[migs647]

What does this PR do? Updates the README on how to use SPM.

Where should the reviewer start? By creating a sample app and adding via the SPM instructions.

How should this be manually tested? ^^^

Any background context you want to provide?

What are the relevant tickets?

Screenshots or screencasts (if UI/UX change)

Questions:

• Does the docs need an update?
  • No
• Are there any security concerns?
  • No
• Do we need to update engineering / success?
  • No