Fix deprecation warning when importing errorban inside the library

`errorban` module [has been deprecated][deprecation] since v0.5.0.
The library continued to use it internally, but because of that, it
was triggering its own deprecation warning. This commit splits
`errorban.nim` into two pieces: the warning and actual code.

[deprecation]: https://github.com/status-im/questionable/commit/e66cd2439b

questionable/errorban.nim

@@ -1,10 +1,3 @@
 {.warning: "errorban is deprecated; use nimble package `upraises` instead".}
 
-## Include this file to indicate that your module does not raise Errors.
-## Disables compiler hints about unused declarations in Nim < 1.4.0
-
-when (NimMajor, NimMinor, NimPatch) >= (1, 4, 0):
-  {.push raises:[].}
-else:
-  {.push raises: [Defect].}
-  {.hint[XDeclaredButNotUsed]: off.}
+include ./private/errorban

questionable/options.nim

@@ -6,7 +6,7 @@ import ./indexing
 import ./operators
 import ./without
 
-include ./errorban
+include ./private/errorban
 
 export options except get
 export binding

questionable/private/errorban.nim

@@ -0,0 +1,8 @@
+## Include this file to indicate that your module does not raise Errors.
+## Disables compiler hints about unused declarations in Nim < 1.4.0
+
+when (NimMajor, NimMinor, NimPatch) >= (1, 4, 0):
+  {.push raises:[].}
+else:
+  {.push raises: [Defect].}
+  {.hint[XDeclaredButNotUsed]: off.}

questionable/results.nim

@@ -8,7 +8,7 @@ import ./operators
 import ./without
 import ./withoutresult
 
-include ./errorban
+include ./private/errorban
 
 export resultsbase except ok, err, isOk, isErr, get
 export binding