feat: add support for bridging gaps between different languages

[horw]

Hello!
This feature has already been implemented in the fork. What do you think about it? Should we create a PR to your repository?
espressif#1

Description

I have used Translation with lang.Merge to bridge the gap between different languages when a specific language version does not exist. For example, if you have the following blogs:

• blog.1.en
• blog.1.ch
• blog.2.en

When you check the English blogs, you will see:

• blog.1.en
• blog.2.en

When you check the Chinese blogs, you will see:

• blog.1.ch
• blog.2.en

[horw]

I found that this will be quite tricky to implement and not very easy to maintain.
So I will close this issue.