chore: Add build tools for translations

Signed-off-by: Wolfgang Walther <walther@technowledgy.de>

README.md

@@ -18,3 +18,21 @@ Once in the nix-shell you have the following commands available:
 
 This documentation is structured according to tutorials-howtos-topics-references. For more details on the rationale of this structure, 
 see https://www.divio.com/blog/documentation.
+
+## Translating
+
+To create `.po` files for translation into a new language pass the language code as the first argument to `postgrest-docs-build`.
+
+Example to add German/de:
+
+```
+postgrest-docs-build de
+```
+
+The livereload server also supports a language/locale argument to show the translated docs during translation:
+
+```
+postgrest-docs-serve de
+```
+
+Spellcheck is currently only available for the default language.