Create IPCC data source

A first example from #18

data-sources/IPCC.md

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+# IPCC Emissions Factor Database
+
+https://www.ipcc-nggip.iges.or.jp/EFDB
+
+Library of emission factors and other parameters with background documentation or technical references.
+For more information, please visit https://ghgprotocol.org/Third-Party-Databases/IPCC-Emissions-Factor-Database
+
+## Details
+
+### Coverage
+
+2002 - present
+
+### Region
+
+Global
+
+### Number of CFs
+
+Unknown, but it seems there are over 22k CFs
+
+### Examples
+