Separate how to add a new language from code change. (#41)

* Separate how to add  a new language from code change.

* Adding pronoun test data if applicable.

documents/how_to_add_new_language.md

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+# How to add a new language support
+
+Adding a new language requires multiple steps:
+1. Adding support for a new locale
+2. Adding inflection rules for the language
+3. Adding lexicon for the language
+
+The following steps with help you identify files that need to be added or changed, and will guide you in rule writing and lexicon preparation.
+
+NOTE: Take a look at [PR #40](https://github.com/unicode-org/inflection/pull/40) for example on how to add initial language support.
+In general, to bootstrap your progress look for grammatically similar language that's already supported, e.g. if you are adding Serbian look for existing Russian or Croatian implementation.
+This will help you find most of the files you need to add/change and will speed up implementation of the rules and lexicons.
+
+## Mark your language as supported
+* UPDATE: morphuntion/src/morphuntion/util/LocaleUtils.hpp
+* UPDATE: morphuntion/src/morphuntion/util/LocaleUtils.cpp
+* UPDATE: morphuntion/test/src/morphuntion/util/LocaleUtilsTest.cpp
+* UPDATE: morphuntion/resources/org/unicode/morphuntion/locale/supported-locales.properties
+* ADD: morphuntion/resources/org/unicode/morphuntion/tokenizer/config_*XX*.properties
+
+## Define language grammar
+* UPDATE: morphuntion/resources/org/unicode/morphuntion/features/grammar.xml
+
+## Add pronouns if applicable
+* ADD: morphuntion/resources/org/unicode/morphuntion/inflection/pronoun_*XX*.csv
+
+## Implement grammar synthesizer for inflecting words and retrieving grammatical properties
+TODO: We need to expand what each of these do.
+* ADD: morphuntion/src/morphuntion/grammar/synthesis/*Xx*GrammarSynthesizer.hpp
+* ADD: morphuntion/src/morphuntion/grammar/synthesis/*Xx*GrammarSynthesizer.cpp
+* ADD: morphuntion/src/morphuntion/grammar/synthesis/*Xx*GrammarSynthesizer_*Xx*DisplayFunction.hpp
+* ADD: morphuntion/src/morphuntion/grammar/synthesis/*Xx*GrammarSynthesizer_*Xx*DisplayFunction.hpp
+* UPDATE: morphuntion/src/morphuntion/grammar/synthesis/GrammarSynthesizerFactory.cpp
+* UPDATE: morphuntion/src/morphuntion/grammar/synthesis/fwd.hpp
+
+## Add language specific properties for lists, quantities and related topics
+* ADD: morphuntion/src/morphuntion/dialog/language/*Xx*CommonConceptFactory.hpp
+* ADD: morphuntion/src/morphuntion/dialog/language/*Xx*CommonConceptFactory.hpp
+* UPDATE: morphuntion/src/morphuntion/dialog/language/fwd.hpp
+
+## Define and create lexion
+TODO: We need to describe how to get Wikidata lexicon and generate the files.
+
+### Add data to test lexicon
+Use our data driven testing approach to test your logic. You'll need to define a small lexicon that covers all test cases for inflection and pronouns (if applicable for the language).
+
+* ADD: morphuntion/test/resources/morphuntion/dialog/inflection/Xx.xml
+* ADD: morphuntion/test/resources/morphuntion/dialog/pronoun/Xx.xml