update the documentation for internationalization (sugarlabs#4337)

Author: walterbender

README.md

@@ -259,6 +259,21 @@ following resources:
 Programmers, please follow these general [guidelines for
 contributions](https://github.com/sugarlabs/sugar-docs/blob/master/src/contributing.md).
 
+### Translators
+
+Music Blocks uses
+[PO files](https://www.gnu.org/software/gettext/manual/html_node/PO-Files.html)
+to maintain translations of the text strings used in the
+interface. The PO files are available through an
+[interactive website](https://weblate.sugarlabs.org/projects/music-blocks/music-blocks/).
+
+Alternatively, translators can clone the
+[git repo](https://github.com/sugarlabs/musicblocks.git), edit the PO files
+locally, and make a pull request.
+
+Note that once the PO files are updated, they are compiled into an INI
+file, which is the file used by Music Blocks.
+
 ### New Contributors
 
 Use the

po/README.md

@@ -5,7 +5,7 @@ We are using PO files as the basic mechanism for managing translation
 of Music Blocks. We'd prefer that translators work with the Sugar
 Labs [Pootle server]( https://weblate.sugarlabs.org) and
 we will work with you to set up a PO file for your language if one is
-not presently on the server. Also feel free to make Pull Requests
+not presently on the server. Also feel free to make pull requests
 directly to this repository with updates to existing (or new) PO
 files.
 
@@ -19,4 +19,26 @@ The string of text goes like this:
 msgid "word_in_English"
 msgstr "put_word_in_translated_language_here"
 
-The text input between the two quotation marks of msgstr will be displayed when a users browser requests the target language
+The text input between the two quotation marks of msgstr will be
+displayed when a users browser requests the target language.
+
+Under the hood
+==============
+
+MusicBlocks.pot is a template that is periodically updated with all of
+the strings used for internationalization. Individual language PO
+files are updated from this POT file.
+
+As per above, translators work with the PO files, either through the
+web interface or by making a pull request.
+
+The localization.ini file is compliled from the PO files. The INI file
+is used by JavaScript to do the actual translation of the interface.
+
+There are instructions for adding a new language to the pull-down menu
+in the
+[README.md](https://github.com/sugarlabs/musicblocks/blob/master/README.md)
+file found in the js directory.
+
+The tools for maintaining the POT, PO, and INI files are found in the
+[PO Utils](https://github.com/sugarlabs/po-utils) repository.