Add missing parameter to atan2 operator (#6142)

* Added missing trigonometrics filter operators

This PR adds support to trigonometry operators, allowing to create spider graphs and other geometric shapes with filters.

* Adds the missing trigonometric filter operators

This PR adds support to the missing trigonometric filter operators (cos, sin, tan, acos, asin, atan, atan2), allowing to create spider graphs, [pie charts, donut charts, polar charts](https://ffoodd.github.io/chaarts/pie-charts.html) and other geometric shapes with filters, which was previously not possible without add-ons.

Example :

`[[2]cos[]] = -0.4161468365471424`

See also this radar chart made in wikitext by @saqimtiaz using the new trigonometric operators :
https://saqimtiaz.github.io/sq-tw/temp/radar-chart-demo.html

* Add documentation for the Trigonometric Operators 

Accompanies code changes #6127

* Fix formatting of atan2 Operator.tid

Removed two empty lines at the end of the tiddler

* Add examples for the trigonometric operators 

Accompanies code changes Jermolene#6127

* Fix version in the doc for trigonometric operators

This PR fix the content of the documentation tiddlers regarding trigonometric operators (#6131). 

<<.from-version "5.1.20">> was changed to <<.from-version "5.1.21">>

* Fix formatting of atan2 Operator.tid

Removed two empty lines at the end of the tiddler

* Add missing parameter to atan2 operator

The atan2 operator needs two parameters (Binary Mathematics Operators), this PR adds the second one that was missing.

See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/atan2 for more technical info on the atan2 function.

core/modules/filters/math.js

@@ -191,7 +191,7 @@ exports.atan = makeNumericBinaryOperator(
 );
 
 exports.atan2 = makeNumericBinaryOperator(
-	function(a) {return Math.atan2(a)}
+	function(a,b) {return Math.atan2(a,b)}
 );
 
 //Calculate the variance of a population of numbers in an array given its mean