coala/docs: Add position number convention

Added a note in Writing_Native_Bears.rst and a reminder
for developers in Writing_Linter_Bears.rst files.

Closes #5297

docs/Developers/Writing_Linter_Bears.rst

@@ -251,6 +251,10 @@ We need to map that to coala's convention as follows:
             normalize_column_numbers = True,
             ...)
 
+This is a reminder for developers that they need to do a proper research on
+linter bear, ensure the convention and ideally write tests to ensure
+that behaviour.
+
 Suggest Corrections Using the ``corrected`` and ``unified-diff`` Output Formats
 -------------------------------------------------------------------------------
 

docs/Developers/Writing_Native_Bears.rst

@@ -598,4 +598,11 @@ For example, let's make an aspect bear named SpellingCheckBear.
                         aspect=DictionarySpelling('py'),
                     )
 
+.. note::
+
+    coala uses 1-based line & column convention, i.e., the first line
+    and first column are 1. However, some linters use 0-based convention.
+    For example, ``pylint`` uses 1-based line convention and 0-based column
+    convention. We need to map these conventions.
+
 .. _main tutorial: https://docs.coala.io/en/latest/Users/Tutorial.html