Bump version to v5.1

src/headers/desc.html

@@ -1,6 +1,6 @@
 <a href="https://github.com/anki-geo/ultimate-geography/"><b>FULL DESCRIPTION</b></a> | <a href="https://github.com/anki-geo/ultimate-geography/releases"><b>RELEASE NOTES</b></a> | <a href="https://github.com/anki-geo/ultimate-geography/blob/master/CONTRIBUTING.md"><b>CONTRIBUTING</b></a>
 
-<b>Ultimate Geography v5.0</b> features:
+<b>Ultimate Geography v5.1</b> features:
 
 - the world's <a href="https://en.wikipedia.org/wiki/List_of_sovereign_states"><b>206 sovereign states</b></a> (824 cards)
 - <b>59 territories, world regions, and other entities</b> (103 cards)

src/headers/desc_es.html

@@ -1,6 +1,6 @@
 <a href="https://github.com/anki-geo/ultimate-geography/"><b>DESCRIPCIÓN COMPLETA</b></a> | <a href="https://github.com/anki-geo/ultimate-geography/releases"><b>NOTAS DE LANZAMIENTO</b></a> | <a href="https://github.com/anki-geo/ultimate-geography/blob/master/CONTRIBUTING.md"><b>CÓMO CONTRIBUIR</b></a>
 
-Características de <b>Ultimate Geography v5.0</b>:
+Características de <b>Ultimate Geography v5.1</b>:
 
 - Los <a href="https://en.wikipedia.org/wiki/List_of_sovereign_states"><b>206 estados soberanos</b></a> del mundo (824 cartas).
 - <b>59 territorios, regiones del mundo, y otras entidades</b> (103 cartas).

src/headers/desc_zh.html

@@ -1,6 +1,6 @@
 <a href="https://github.com/anki-geo/ultimate-geography/"><b>完整说明</b></a> | <a href="https://github.com/anki-geo/ultimate-geography/releases"><b>发行说明</b></a> | <a href="https://github.com/anki-geo/ultimate-geography/blob/master/CONTRIBUTING.md"><b>贡献指南</b></a>
 
-<b>Ultimate Geography v5.0</b> 特性:
+<b>Ultimate Geography v5.1</b> 特性:
 
 - 全世界 <a href="https://en.wikipedia.org/wiki/List_of_sovereign_states"><b>206 个主权国家</b></a> (824 张卡片)
 - <b>59 个领土、世界区域和其他实体</b> (103 张卡片)