Merge pull request #2 from vannkorn/ldp-build

- Add sound.html
- fix gab between hero image and main menu
- fix error tab content in sound.html
Merge pull request #3 from vannkorn/fix_bug

- fix gab between hero image and main menu
- add mp3 player to home page (static) using jplayer
Merge pull request #4 from vannkorn/fix_bug

- add mp3 player to home page (static) using jplayer
- add download functionality
Merge pull request #5 from vannkorn/fix_bug

- add download functionality
- change សំលេង toសំឡេង
- make running letters for test
- align main menu to center