Fix Params case handling in the index, sort and where func

This means that you can now do:

```
{{ range where .Site.Pages "Params.MYPARAM" "foo" }}
```

3 files changed, 6 insertions, 4 deletions

diff --git a/resources/page/page_nop.go b/resources/page/page_nop.go
index ea1a44d8f..09ac136fc 100644
--- a/resources/page/page_nop.go
+++ b/resources/page/page_nop.go
@@ -300,7 +300,7 @@ func (p *nopPage) Param(key interface{}) (interface{}, error) {
 	return nil, nil
 }
 
-func (p *nopPage) Params() map[string]interface{} {
+func (p *nopPage) Params() maps.Params {
 	return nil
 }
 
diff --git a/resources/page/site.go b/resources/page/site.go
index 9153c8556..31058637b 100644
--- a/resources/page/site.go
+++ b/resources/page/site.go
@@ -17,6 +17,8 @@ import (
 	"html/template"
 	"time"
 
+	"github.com/gohugoio/hugo/common/maps"
+
 	"github.com/gohugoio/hugo/config"
 
 	"github.com/gohugoio/hugo/common/hugo"
@@ -39,7 +41,7 @@ type Site interface {
 	Taxonomies() interface{}
 	LastChange() time.Time
 	Menus() navigation.Menus
-	Params() map[string]interface{}
+	Params() maps.Params
 	Data() map[string]interface{}
 }
 
@@ -107,7 +109,7 @@ func (t testSite) BaseURL() template.URL {
 	return ""
 }
 
-func (t testSite) Params() map[string]interface{} {
+func (t testSite) Params() maps.Params {
 	return nil
 }
 
diff --git a/resources/page/testhelpers_test.go b/resources/page/testhelpers_test.go
index 560166b0b..cc6a74f06 100644
--- a/resources/page/testhelpers_test.go
+++ b/resources/page/testhelpers_test.go
@@ -370,7 +370,7 @@ func (p *testPage) Param(key interface{}) (interface{}, error) {
 	return resource.Param(p, nil, key)
 }
 
-func (p *testPage) Params() map[string]interface{} {
+func (p *testPage) Params() maps.Params {
 	return p.params
 }