Add unified API landing page and fix footer layout (#1169) #4339

Job	Run time
Lint Gate	1m 15s
Detect File Changes	9s
Github (ubuntu, mpi, debug, true)	1h 59m 36s
Github (macos, mpi, debug, false)	1h 10m 9s
Georgia Tech \| Phoenix (cpu)	1h 15m 38s
Github (ubuntu, mpi, no-debug, false)	2h 15m 35s
Github (ubuntu, mpi, debug, false)	2h 6m 50s
Oak Ridge \| Frontier (cpu)	1s
Oak Ridge \| Frontier (gpu-omp)	2h 22m 20s
Oak Ridge \| Frontier (AMD) (gpu-omp)	8m 42s
Oak Ridge \| Frontier (AMD) (cpu)	2h 22m 20s
Github (macos, mpi, no-debug, false)	1h 28m 55s
Georgia Tech \| Phoenix (gpu-omp)	1h 34m 1s
Oak Ridge \| Frontier (gpu-acc)	1s
Github (ubuntu, mpi, no-debug, true)	1h 33m 59s
Github (ubuntu, no-mpi, single, no-debug, false)	29m 33s
Georgia Tech \| Phoenix (gpu-acc)	49m 15s
	19h 38m 19s

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