Correct all eggs (#15906)

* "eg" is a misspelled "egg", "e.g." is "exempli gratia"
* Also, "ie" is "i.e.".

nimdoc/testproject/testproject.nim

@@ -49,7 +49,7 @@ proc isValid*[T](x: T): bool = x.len > 0
 
 when true:
   # these cases appear redundant but they're actually (almost) all different at
-  # AST level and needed to ensure docgen keeps working, eg because of issues
+  # AST level and needed to ensure docgen keeps working, e.g. because of issues
   # like D20200526T163511
   type
     Foo* = enum