lsp: Add workspace/applyEdit to client capabilites

[sudormrfbin]

The functionality already existed, but the capability wasn't being reported correctly to the server:

helix/helix-term/src/application.rs

Lines 716 to 728 in 230ba26

	MethodCall::ApplyWorkspaceEdit(params) => {
	apply_workspace_edit(
	&mut self.editor,
	helix_lsp::OffsetEncoding::Utf8,
	&params.edit,
	);
	Ok(json!(lsp::ApplyWorkspaceEditResponse {
	applied: true,
	failure_reason: None,
	failed_change: None,
	}))
	}