Create a struct with all of Hugo's config options

Primary motivation is documentation, but it will also hopefully simplify the code.

Also,

* Lower case the default output format names; this is in line with the custom ones (map keys) and how
it's treated all the places. This avoids doing `stringds.EqualFold` everywhere.

Closes #10896
Closes #10620

tpl/data/resources.go

@@ -24,7 +24,6 @@ import (
 
 	"github.com/gohugoio/hugo/cache/filecache"
 
-	"github.com/gohugoio/hugo/config"
 	"github.com/gohugoio/hugo/helpers"
 	"github.com/spf13/afero"
 )
@@ -100,8 +99,8 @@ func (ns *Namespace) getRemote(cache *filecache.Cache, unmarshal func([]byte) (b
 }
 
 // getLocal loads the content of a local file
-func getLocal(url string, fs afero.Fs, cfg config.Provider) ([]byte, error) {
-	filename := filepath.Join(cfg.GetString("workingDir"), url)
+func getLocal(workingDir, url string, fs afero.Fs) ([]byte, error) {
+	filename := filepath.Join(workingDir, url)
 	return afero.ReadFile(fs, filename)
 }
 
@@ -114,7 +113,7 @@ func (ns *Namespace) getResource(cache *filecache.Cache, unmarshal func(b []byte
 		if err != nil {
 			return err
 		}
-		b, err := getLocal(url, ns.deps.Fs.Source, ns.deps.Cfg)
+		b, err := getLocal(ns.deps.Conf.BaseConfig().WorkingDir, url, ns.deps.Fs.Source)
 		if err != nil {
 			return err
 		}