feat: add the data function to fetch data from page data or site data (#40)

Author: razonyang

layouts/partials/base/functions/data.html

@@ -0,0 +1,15 @@
+{{- $v := false }}
+{{- $key := replace .key "." "/" | printf "%s.{toml,yaml,yml,json}" }}
+{{- with .page.Resources.GetMatch $key }}
+  {{- $v = .Content | transform.Unmarshal }}
+{{- else }}
+  {{- $data := site.Data }}
+  {{- $keys := split .key "." }}
+  {{- range $keys }}
+    {{- with index $data . }}
+      {{- $data = . }}
+      {{- $v = . }}
+    {{- end }}
+  {{- end }}
+{{- end }}
+{{- return $v -}}