v1.9.0

ModelingToolkitStandardLibrary v1.9.0

Diff since v1.8.0

Merged pull requests:

• add closed-loop analysis to DC-motor tutorial (#124) (@baggepinnen)
• reproducible docs (#126) (@ArnoStrouwen)
• spelling (#127) (@ArnoStrouwen)
• [skip ci] doc compat (#128) (@ArnoStrouwen)
• implement linearize using linearization_function (#129) (@baggepinnen)
• Allow loop openings in all sensitivity functions (#131) (@baggepinnen)