OrphanTypeDeclaration Error explaination (#395)

* OrphanTypeDeclaration Error explaination

Doing my part to fill in some documentation

* Fixed typos

* Wording change requested by Jordan Martinez

"How about 'This is often caused by typographical issues.' ?"

* Style Guide change: PureScript

Use appropriate capitalization of `PureScript`

Co-authored-by: Harry Garrood <[email protected]>

* Rephrase 'typographical issues' to 'spelling mistakes'

Co-authored-by: Harry Garrood <[email protected]>

Co-authored-by: Harry Garrood <[email protected]>
Co-authored-by: JordanMartinez <[email protected]>

Author: 3 people

errors/OrphanTypeDeclaration.md

@@ -5,17 +5,23 @@
 ```purescript
 module ShortFailingExample where
 
+addTwo :: Number -> Number -> Number
+addToo a b = a + b
 ...
 ```
 
 ## Cause
 
-Explain why a user might see this error.
+Purescript requires that the type declaration for a function or value (i.e. the line with the `::` in it)
+be followed immediately by the definition of that function or value (i.e. the line with the `=` in it). The
+compiler has found a declaration for which a definition did not follow.
 
-## Fix
-
-- Suggest possible solutions.
+This is often caused by spelling mistakes.  Check to see that the declaration and the
+definition are spelled the same. PureScript is a whitespace sensitive language and the presence of an
+extra space can make the definition look like a part of the declaration.
 
-## Notes
+## Fix
 
-- Additional notes.
+- Ensure that the next (non-comment) line is the definition for the listed declaration.
+- Check that the spelling of the two matches.
+- Check for extra spaces.  Both declaration and definition should start with the same indentation.