Convert example to exemplar

* Rename example files to exemplar

See exercism/docs#23

* [Docs] Correct .meta/example references to .meta/exemplar

* [Docs] Use exemplar instead of example

* [Docs] Update example name in file listings

* [Julia] Convert to exemplar.jl

* [elm] Rename .meta/Cook.elm to .meta/Examplar.elm

* [elm] Rename .meta/Examplar.elm .meta/Exemplar.elm

Co-authored-by: Matthieu Pizenberg <[email protected]>

reference/implementing-a-concept-exercise.md

@@ -18,7 +18,7 @@ languages
                 |   └── hints.md
                 ├── .meta
                 |   |── design.md
-                |   └── Example.el
+                |   └── Exemplar.el
                 ├── <NAME>.el
                 └── <NAME>_test.el
 ```