Added new guide for using index templates with the low-level client. … #1042

Job	Run time
Integration OpenSearch (2.9.0)	10m 50s
Integration OpenSearch Unreleased (1.x)	5m 18s
Integration OpenSearch (2.8.0)	8m 14s
Integration OpenSearch Unreleased (2.x)	16m 9s
Integration OpenSearch (2.7.0)	7m 51s
Integration OpenSearch Unreleased (main)	20m 41s
Integration OpenSearch (2.6.0)	8m 4s
Integration OpenSearch (2.5.0)	8m 31s
Integration OpenSearch (2.4.1)	7m 36s
Integration OpenSearch (2.3.0)	7m 26s
Integration OpenSearch (2.2.1)	7m 18s
Integration OpenSearch (2.1.0)	7m 25s
Integration OpenSearch (2.0.1)	8m 46s
Integration OpenSearch (1.3.11)	7m 47s
Integration OpenSearch (1.2.4)	7m 38s
Integration OpenSearch (1.1.0)	8m 58s
	2h 28m 32s

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