tpl: Add hasSuffix alias

strings.HasPrefix already has an alias of hasPrefix
but strings.HasSuffix has no such alias.
This PR adds a hasSuffix alias to the tpl function with corresponding
function documentation.
It also adds a Minor update to the hasPrefix function documentation
re: keywords and relatedfuncs.

 Completes https://github.com/gohugoio/hugo/issues/10474

docs/content/en/functions/hasPrefix.md

@@ -9,11 +9,11 @@ categories: [functions]
 menu:
   docs:
     parent: "functions"
-keywords: []
+keywords: [strings]
 signature: ["hasPrefix STRING PREFIX"]
 workson: []
 hugoversion:
-relatedfuncs: []
+relatedfuncs: [hasSuffix]
 deprecated: false
 aliases: []
 ---