SDG Indicators should include example format in description (as Targets and Goals to)

[stevieflow]

Minor minor thing, but could be helpful for users

Targets and Goals include an example of the format in the description - eg:

SDG Goal	A value from the top-level list of UN sustainable development goals (SDGs) (e.g. ‘1’)

SDG Target	A value from the second-level list of UN sustainable development goals (SDGs) (e.g. ‘1.1’)

This is missing from the Indicator :

SDG Indicator	A value from the second-level list of UN sustainable development (SDG) indicators

It would be useful to add this, for consistency and support

[stevieflow]

Fix made, and PR created