docs, external: introduce `langchain-localai` #35350

Job	Run time
build	11s
cd ${{ matrix.job-configs.working-directory }}	0s
cd ${{ matrix.job-configs.working-directory }}	0s
cd ${{ matrix.job-configs.working-directory }} / make extended_tests #${{ matrix.job-configs.python-version }}	0s
cd ${{ matrix.job-configs.working-directory }}	0s
test-doc-imports (3.12) / check doc imports #3.12	52s
cd . / make lint #3.9	49s
cd . / make lint #3.12	43s
CI Success	1s
	2m 36s

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