Add optional QuickSymbols IPC support

[LatencyBryer]

This pull request introduces QuickSymbols plugin IPC integration for ChatTwo.

Essentially, the aim is to enable ChatTwo users to launch the QuickSymbols popup-list when the ChatTwo input is focused, pick symbols and then have ChatTwo place those chosen symbols into its own text entry field.

ChatTwo has its own text input, focus, selection and caret state, so the safest integration is for ChatTwo to opt in via IPC and perform the final insertion on its side.

How it works

No clipboard, synthetic input or external ImGui input writing is used.
ChatTwo monitors its own input while active and informs QuickSymbols via QuickSymbols.WatchInput.

Upon pressing the QuickSymbols keybind it will open its own popup for the ChatTwo owner. When you select a symbol, QuickSymbols sends it back through QuickSymbols.SymbolSelected and ChatTwo inserts it through its own text input handler.

Changes Made

• Added a small QuickSymbolsIpc integration class
• Registers optional QuickSymbols IPC subscribers
• Lets ChatTwo advertise its active input through QuickSymbols.WatchInput
• Receives selected symbols through QuickSymbols.SymbolSelected
• Inserts symbols through ChatTwo own input path

Notes

The integration is completely optional. If QuickSymbols is not installed, not loaded or does not expose the expected IPC, ChatTwo will continue to work normally.
If you want, you can get the full QuickSymbols/IPC documentation I wrote here.

QuickSymbols IPC support itself is currently pending in a separate Dalamud plugin PR. This integration with ChatTwo will only become active in-game once that update is merged. (Jun 15, 07:04 PM EST)
QuickSymbols IPC support merged on Stable. (Jun 15, 10:45 PM EST)