Expose a new command argument for `allowInlineDiffs`

[jtpio]

An issue to track the following TODO:

jupyterlab-diff/src/diff/utils.ts

Lines 44 to 45 in d9dcd67

	// TODO: make configurable
	// allowInlineDiffs: true,

@codemirror/merge has an option to allow inline diffs: https://codemirror.net/docs/ref/#merge.unifiedMergeView^config.allowInlineDiffs

It would be great to expose that as an optional command argument (maybe still defaulting to false for now).