[Content] Add content from Discord (#cpp, #projects, #problems, etc)

[karnkaul]

• Figure out structure for post categories, menus, search, etc
• Transfer content
• Fix up Topics
• Add post about CMake (targets, strings, configure/generate, etc)
  • Script syntax
  • Variables, strings, lists
  • Functions, conditional flow
  • Targets, properties, scope
  • Configuration, generators
  • Compilers, linkers, make programs
  • Book link
• Git branching / repository setup for C++
  • One repo = one project, multiple environments
  • Build + config setup
  • Branching strategy