Tidy up precipitation (#3023)

Fixes #2953

This is an attempt to fix the issue with precipitation amount and
percentage mixup. I have created a separate
`precipitationPercentage`-variable where the probability of rain can be
stored.

The config options now has the old `showPrecipitationAmount` in addition
to a new setting: `showPrecipitationProbability` (shows the likelihood
of rain).

<details>
  <summary>Examples</summary>
  
  ### Yr

I tested the Yr weather provider for a Norwegian city Bergen that has a
lot of rain. I have removed properties that are irrelevant for this demo
from the config-samples below.

Config:
  ```js
{
	module: "weather",
	config: {
			weatherProvider: "yr",
			type: "current",
			showPrecipitationAmount: true,
			showPrecipitationProbability: true
	}
},
{
	module: "weather",
	config: {
			weatherProvider: "yr",
			type: "hourly",
			showPrecipitationAmount: true,
			showPrecipitationProbability: true
	}
},
{
	module: "weather",
	config: {
			weatherProvider: "yr",
			type: "daily",
			showPrecipitationAmount: true,
			showPrecipitationProbability: true
	}
}
  ```

Result:<br/>
<img width="444" alt="screenshot"
src="https://user-images.githubusercontent.com/34011212/216775423-4e37345c-f915-47e5-8551-7c544ebd24b1.png">

</details>

---------

Co-authored-by: Magnus Marthinsen <magmar@online.no>
Co-authored-by: Veeck <github@veeck.de>

tests/e2e/modules/weather_hourly_spec.js

@@ -33,4 +33,32 @@ describe("Weather module: Weather Hourly Forecast", () => {
 			}
 		});
 	});
+
+	describe("Show precipitations", () => {
+		beforeAll(async () => {
+			await weatherFunc.startApp("tests/configs/modules/weather/hourlyweather_showPrecipitation.js", {});
+		});
+
+		describe("Shows precipitation amount", () => {
+			const amounts = [undefined, undefined, undefined, "0.13 mm", "0.13 mm"];
+			for (const [index, amount] of amounts.entries()) {
+				if (amount) {
+					it(`should render precipitation amount ${amount}`, async () => {
+						await weatherFunc.getText(`.weather table.small tr:nth-child(${index + 1}) td.precipitationAmount`, amount);
+					});
+				}
+			}
+		});
+
+		describe("Shows precipitation propability", () => {
+			const propabilities = [undefined, undefined, "12%", "36%", "44%"];
+			for (const [index, pop] of propabilities.entries()) {
+				if (pop) {
+					it(`should render propability ${pop}`, async () => {
+						await weatherFunc.getText(`.weather table.small tr:nth-child(${index + 1}) td.precipitationProbability`, pop);
+					});
+				}
+			}
+		});
+	});
 });