Plugin SDK: add more comments and examples

plugins/sdk/src/main/java/de/mm20/launcher2/sdk/weather/Forecast.kt

@@ -1,5 +1,14 @@
 package de.mm20.launcher2.sdk.weather
 
+/**
+ * Temperature value.
+ * Use [Double].[C], [Double].[F] or [Double].[K] to create a temperature value:
+ * ```kt
+ * val temp = 20.0.C
+ * val temp2 = 68.0.F
+ * val temp3 = 293.15.K
+ * ```
+ */
 @JvmInline
 value class Temperature internal constructor(internal val kelvin: Double)
 
@@ -21,6 +30,15 @@ val Double.F
 val Double.K
     get() = Temperature(this)
 
+/**
+ * Wind speed value.
+ * Use [Double].[m_s], [Double].[km_h] or [Double].[mph] to create a wind speed value:
+ * ```kt
+ * val wind = 5.0.m_s
+ * val wind2 = 18.0.km_h
+ * val wind3 = 11.1847.mph
+ * ```
+ */
 @JvmInline
 value class WindSpeed internal constructor(internal val metersPerSecond: Double)
 
@@ -42,6 +60,14 @@ val Double.km_h
 val Double.mph
     get() = WindSpeed(this * 0.44704)
 
+/**
+ * Pressure value.
+ * Use [Double].[hPa] or [Double].[mbar] to create a pressure value:
+ * ```kt
+ * val pressure = 1013.25.hPa
+ * val pressure2 = 1013.25.mbar
+ * ```
+ */
 @JvmInline
 value class Pressure internal constructor(internal val hPa: Double)