Setting project to Wikimedia-Site-requests, as this request is about settings / configuration of a Wikimedia website.

For more information about how to request these kinds of changes, please see https://meta.wikimedia.org/wiki/Requesting_wiki_configuration_changes

...and if you feel like writing a patch for adding those namespace aliases yourself:
The file to change is wmf-config/InitialiseSettings.php in the repository operations/mediawiki-config for Wikimedia, and https://phabricator.wikimedia.org/source/mediawiki/browse/master/languages/messages/MessagesMs.php (Hmm, I admit I'm not sure myself if both files need to be changed here, to be honest.)

Please discuss it with you local community first and give us a link to that discussion. Also is your wiki big enough to manage content in that namespaces?

In T160350#3095821, @Aklapper wrote:

...and if you feel like writing a patch for adding those namespace aliases yourself:
The file to change is wmf-config/InitialiseSettings.php in the repository operations/mediawiki-config for Wikimedia, and https://phabricator.wikimedia.org/source/mediawiki/browse/master/languages/messages/MessagesMs.php (Hmm, I admit I'm not sure myself if both files need to be changed here, to be honest.)

I think only the first need to be changed.

In T160350#3095822, @Urbanecm wrote:

Please discuss it with you local community first and give us a link to that discussion. Also is your wiki big enough to manage content in that namespaces?

Well, it is not that big... but I am really appreciate to have all or some of the namespaces, especially:
Appendix = Lampiran
Summary = Ringkasan
Citations = Petikan
Index = Indeks
Rhymes = Rima
Reconstruction = Rekonstruksi

But yeah... I have no rights to do it. Is there anyway that I can get a rights to change all the way to .php file?

You need just account at wikitech, then continue according to the manual Aklapper linked. When in doubt ask But even you write a patch yourself the consensus is really needed as well as enough size of the community. The patch won't be merged if some of these conditions are not met.

But I can change the files myself if you wish. But I can't work on conditions I described as I do not know your project, community etc.