[Content] Add devnet details (#40)

* content - Add devnet details
 - Description in examples section
 - Glossary entry and updated testnet/regtest

* content - Devnet P2P
 - Add to start string and spork key tables

Closes #36

_data/glossary/en/devnet.yaml

@@ -0,0 +1,32 @@
+---
+# This file is licensed under the MIT License (MIT) available on
+# http://opensource.org/licenses/MIT.
+
+required:
+                                           #-------------40 characters-------------#
+    title_max_40_characters_no_formatting: Devnet, Development Network
+
+    summary_max_255_characters_no_formatting: >
+        A development environment in which developers can obtain and
+        spend duffs that have no real-world value on a network that
+        is very similar to the Dash mainnet. Multiple independent devnets can
+        coexist without interference. Devnets can be either public or private.
+
+    synonyms_shown_in_glossary_capitalize_first_letter:
+        - Devnet
+
+optional:
+    synonyms_and_pluralizations_not_shown_in_glossary:
+        - devnets
+        - devnets mode
+        - devnets modes
+        - development network
+
+    not_to_be_confused_with_capitalize_first_letter:
+        - Regtest (a local testing environment where developers can control block generation)
+        - Testnet (a global testing environment which mostly mimics mainnet)
+
+    links_html_or_markdown_style_capitalize_first_letter:
+        - "[Devnet mode](/en/developer-examples#devnet-mode) --- Developer Examples"
+
+---