Add `.shopify/metafields.json` to `.gitignore` by default #17738

Job	Run time
[PR] Run build with Node 18.20.3 in ubuntu-latest	54s
[Main] Node ${{ matrix.node }} in ${{ matrix.os }}	0s
[PR] Run bundle with Node 18.20.3 in ubuntu-latest	1m 17s
[PR] Run type-check with Node 18.20.3 in ubuntu-latest	1m 26s
[PR] Run lint with Node 18.20.3 in ubuntu-latest	1m 57s
[PR] Check graphql-codegen has been run (macos-latest, 18.20.3)	1m 56s
[PR] Run knip with Node 18.20.3 in ubuntu-latest	34s
[PR] Check OCLIF manifests & readme & docs	2m 22s
[PR] Accept. Test with Node 18.20.3 in ubuntu-latest	4m 47s
[PR] Accept. Test with Node 18.20.3 in macos-latest	4m 25s
[PR] Accept. Test with Node 18.20.3 in windows-latest	2m 5s
[PR] Run Test Coverage with Node 18.20.3 in ubuntu-latest	3m 57s
[PR] Test with Node 18.20.3 in ubuntu-latest	3m 25s
[PR] Test with Node 20.14.0 in ubuntu-latest	3m 9s
[PR] Test with Node 22.2.0 in ubuntu-latest	3m 2s
[Manual] Test with Node ${{ inputs.node-version }} in ${{ inputs.os }}	0s
[PR] Test with Node 18.20.3 in windows-latest	5m 47s
[PR] Test with Node 20.14.0 in windows-latest	6m 53s
[PR] Test with Node 22.2.0 in windows-latest	5m 48s
[PR] Test with Node 18.20.3 in macos-latest	3m 44s
[PR] Test with Node 20.14.0 in macos-latest	3m 4s
[PR] Test with Node 22.2.0 in macos-latest	2m 41s
	1h 3m 13s

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