Add index entries for GHC-67120, GHC-89246, and GHC-94803

[jllang]

No description provided.

[Bodigrim]

Suggested change

	According to the second paragraph of Chapter 5 of The Haskell 98 Report,
	According to the second paragraph of Chapter 5 of [The Haskell 2010 Report](https://www.haskell.org/onlinereport/haskell2010/haskellch5.html#x11-980005),

[Bodigrim]

Suggested change

> A Haskell program is a collection of modules, one of which, by convention, must be called Main and must export the value main. The value of the program is the value of the identifier main in module Main, which must be a computation of type IO t for some type t (see Chapter 7). When the program is executed, the computation main is performed, and its result (of type t) is discarded.

> A Haskell program is a collection of modules, one of which, by convention, must be called `Main` and must export the value `main`. The value of the program is the value of the identifier `main` in module `Main`, which must be a computation of type `IO t` for some type `t` (see Chapter 7). When the program is executed, the computation `main` is performed, and its result (of type `t`) is discarded.

[Bodigrim]

Could you please fill the title?

[Bodigrim]

My experience is that it's far more common reason for GHC-67120 that you meant to write a library exporting notMain, in which case the solution is to rename module Main to module Lib or anything.

What contributes to the problem is that GHC would assume module Main where implicitly unless there is module declaration.

Probably worth adding another example or at least discussing this case in index.md.