Cannot type some Sinhala characters with the Wijesekera kayboard layout in fcitx-m17n

[lohang]

Describe the bug
Some Sinhala characters are missing from the Wijesekera keyboard layout in fcitx-m17n. These are the missing characters (and corresponding keys in the US keyboard) I've found:

ථ = :
ඥ = {
ළ = <
: = }
, = "

To Reproduce
Steps to reproduce the behavior:

1. Start a text editor (emacs)
2. Switch to wijesekera (M17N)
3. Try to type these keys
   :
   {
   <
   }
   "

Expected behavior
These are the characters that should correspond to the above keys:

ථ = :
ඥ = {
ළ = <
: = }
, = "

Desktop:

• Desktop: GNOME 3.28.2, Ubuntu 18.04.5
• Display server type: X11

Additional information
This is the full layout of the Wijesekera keyboard.