all: Fix spelling

And some other minor issues.

tpl/internal/templatefuncsRegistry.go

@@ -84,7 +84,7 @@ type TemplateFuncMethodMapping struct {
 	Method interface{}
 
 	// Any template funcs aliases. This is mainly motivated by keeping
-	// backwards compability, but some new template funcs may also make
+	// backwards compatibility, but some new template funcs may also make
 	// sense to give short and snappy aliases.
 	// Note that these aliases are global and will be merged, so the last
 	// key will win.

tpl/math/math.go

@@ -92,7 +92,7 @@ func (ns *Namespace) Mul(a, b interface{}) (interface{}, error) {
 	return DoArithmetic(a, b, '*')
 }
 
-// Sub substracts two numbers.
+// Sub subtracts two numbers.
 func (ns *Namespace) Sub(a, b interface{}) (interface{}, error) {
 	return DoArithmetic(a, b, '-')
 }