Add payment requests

BTCPayServer/wwwroot/payment-request/helpers/math.js

@@ -0,0 +1,17 @@
+Number.prototype.noExponents= function(){
+    var data= String(this).split(/[eE]/);
+    if(data.length== 1) return data[0];
+
+    var  z= '', sign= this<0? '-':'',
+        str= data[0].replace('.', ''),
+        mag= Number(data[1])+ 1;
+
+    if(mag<0){
+        z= sign + '0.';
+        while(mag++) z += '0';
+        return z + str.replace(/^\-/,'');
+    }
+    mag -= str.length;
+    while(mag--) z += '0';
+    return str + z;
+};