add Japanese translations of NFT-related pages

- fix NFTokenOffer JSON Type to use `Currency Amount` instead `object or string`
- incremental reserve to 2 XRP
- Corrected description of failure conditions at Direct Mode
-

content/_snippets/rippled-api-links.md

@@ -239,4 +239,5 @@
 
 {% for amd in amendment_names %}
 [{{amd}} amendment]: known-amendments.html#{{amd|lower}}
+[{{amd}}の修正]: known-amendments.html#{{amd|lower}}
 {% endfor %}