docs: add FlytePlugins architecture image #1350

Job	Run time
unpack-envvars	1s
Docker Build Images (datacatalog) / build_docker	1m 56s
Docker Build Images (flyteadmin) / build_docker	2m 25s
Docker Build Images (flytepropeller) / build_docker	2m 45s
Docker Build Images (flytecopilot) / build_docker	1m 50s
Build Images / Build & Push Image (datacatalog) / Push to Github Registry	2m 28s
Build Images / Build & Push Image (flyteadmin) / Push to Github Registry	3m 9s
Build Images / Build & Push Image (flytecopilot) / Push to Github Registry	2m 26s
Build Images / Build & Push Image (flytepropeller) / Push to Github Registry	4m 8s
Build Images / Build & Push Image (flytescheduler) / Push to Github Registry	3m 19s
Check Go Generate (flytepropeller) / Go Generate	2m 27s
Check Go Generate (flyteadmin) / Go Generate	2m 32s
Check Go Generate (flytecopilot) / Go Generate	1m 9s
Check Go Generate (datacatalog) / Go Generate	1m 25s
Lint (datacatalog) / Run Lint	2m 26s
Lint (flyteadmin) / Run Lint	3m 18s
Lint (flyteidl) / Run Lint	1m 53s
Lint (flyteplugins) / Run Lint	3m 3s
Lint (flytepropeller) / Run Lint	3m 12s
Unit Tests (datacatalog) / Run Unit Test	2m 53s
Lint (flytestdlib) / Run Lint	2m 42s
Unit Tests (flyteadmin) / Run Unit Test	4m 24s
Unit Tests (flytecopilot) / Run Unit Test	2m 30s
Unit Tests (flytepropeller) / Run Unit Test	4m 2s
Unit Tests (flytestdlib) / Run Unit Test	3m 49s
Unit Tests (flyteplugins) / Run Unit Test	3m 53s
Integration Test (flyteadmin) / Integration tests	4m 42s
	1h 14m 47s

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