docs: docs of using ImageSpec in ContainerTask (#6095) #5730

Job	Run time
unpack-envvars	1s
flyteadmin integration tests image / build_docker	4m 40s
Build Images / Build & Push Image (flyteadmin) / Push to Github Registry	5m 51s
Build Images / Build & Push Image (datacatalog) / Push to Github Registry	4m 35s
Build Images / Build & Push Image (flytecopilot) / Push to Github Registry	4m 10s
Build Images / Build & Push Image (flytepropeller) / Push to Github Registry	32s
Build Images / Build & Push Image (flytescheduler) / Push to Github Registry	5m 33s
Dry Run Goreleaser	7m 23s
Test Getting started	7m 35s
Check Go Generate (datacatalog) / Go Generate	2m 32s
Check Go Generate (flyteadmin) / Go Generate	2m 19s
Check Go Generate (flytecopilot) / Go Generate	1m 37s
Check Go Generate (flytectl) / Go Generate	2m 18s
Lint (datacatalog) / Run Lint	2m 34s
Lint (flyteadmin) / Run Lint	3m 16s
Lint (flytecopilot) / Run Lint	2m 3s
Check Go Generate (flytepropeller) / Go Generate	2m 23s
Lint (flytectl) / Run Lint	2m 47s
Lint (flyteidl) / Run Lint	2m 5s
Lint (flyteplugins) / Run Lint	3m 14s
Lint (flytepropeller) / Run Lint	3m 19s
Lint (flytestdlib) / Run Lint	2m 45s
Unit Tests (datacatalog) / Run Unit Test	3m 2s
Unit Tests (flyteadmin) / Run Unit Test	4m 37s
Unit Tests (flytecopilot) / Run Unit Test	2m 51s
Unit Tests (flytectl) / Run Unit Test	3m 41s
Unit Tests (flyteplugins) / Run Unit Test	4m 7s
Unit Tests (flytepropeller) / Run Unit Test	4m 32s
Unit Tests (flytestdlib) / Run Unit Test	3m 46s
Integration Test (flyteadmin) / Integration tests	5m 41s
	1h 45m 49s

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