$ git submodule add https://github.com/dudung/butiran-frontend.git static/js
Cloning into 'M:/butiran/static/js'...
remote: Enumerating objects: 41, done.
remote: Counting objects: 100% (41/41), done.
remote: Compressing objects: 100% (35/35), done.
remote: Total 41 (delta 8), reused 0 (delta 0), pack-reused 0 (from 0)
Receiving objects: 100% (41/41), 111.98 KiB | 319.00 KiB/s, done.
Resolving deltas: 100% (8/8), done.
warning: in the working copy of '.gitmodules', LF will be replaced by CRLF the next time Git touches it

$ git add .gitmodules static/js

$ git commit -a -m "add js submodule"
[main a7d2cfc] add js submodule
 2 files changed, 4 insertions(+)
 create mode 100644 .gitmodules
 create mode 160000 static/js

$ git push
Enumerating objects: 6, done.
Counting objects: 100% (6/6), done.
Delta compression using up to 16 threads
Compressing objects: 100% (4/4), done.
Writing objects: 100% (4/4), 449 bytes | 449.00 KiB/s, done.
Total 4 (delta 1), reused 0 (delta 0), pack-reused 0
remote: Resolving deltas: 100% (1/1), completed with 1 local object.
To https://github.com/dudung/butiran
   a3317d7..a7d2cfc  main -> main