Text Rendering in scene

[athanggupte]

Currently, text rendering can only be done in the ImGui context and not in the actual 3D scene. By stealing a few functions from the ImGui library we can directly incorporate font rendering into the Renderer2D.

Proposed architecture:

1. Wrapper class Apex::FontAtlas over ImFontAtlas
2. Wrapper class Apex::FontGlyph over ImGlyph
3. Create OpenGLTexture2D and set data from ImFontAtlas->GetTexDataAsRGBA32. Set this in ImFontAtlas->SetTexID()
4. Functions Renderer2D::DrawGlyph() which should take in an Apex::FontGlyph and sets the quad attributes accordingly { position, color, UVs, texture index }
5. Helper function Renderer2D::DrawText() which takes in a string and adds all the glyphs in it using similar method as in Renderer2D::DrawGlyph()

Reference links:

• https://discourse.dearimgui.org/t/how-to-steal-glyphs-from-a-imfontatlas/265
• https://learnopengl.com/In-Practice/Text-Rendering

[athanggupte]

Implemented in 41e091837f62166fa4c5be6a335df04c9605152c