Add decimeter as unit of length

Close #650

data/unitconverter/src/main/java/de/mm20/launcher2/unitconverter/converters/LengthConverter.kt

@@ -18,6 +18,11 @@ class LengthConverter(context: Context) : SimpleFactorConverter() {
                     context.getString(R.string.unit_kilometer_symbol),
                     R.plurals.unit_kilometer
             ),
+            MeasureUnitWithFactor(
+                    10.0,
+                    context.getString(R.string.unit_decimeter_symbol),
+                    R.plurals.unit_decimeter
+            ),
             MeasureUnitWithFactor(
                     100.0,
                     context.getString(R.string.unit_centimeter_symbol),

data/unitconverter/src/main/java/de/mm20/launcher2/unitconverter/converters/SimpleFactorConverter.kt

@@ -7,7 +7,7 @@ import de.mm20.launcher2.unitconverter.MeasureUnit
 import de.mm20.launcher2.unitconverter.UnitValue
 
 /**
- * A converter for units that can converted into each other by simply multiplicating with a constant factor
+ * A converter for units that can converted into each other by simple multiplication with a constant factor
  */
 abstract class SimpleFactorConverter: Converter {
     open val standardUnits: List<MeasureUnitWithFactor> = emptyList()