A sample config:
```toml
defaultContentLanguage = "en"
defaultContentLanguageInSubdir = true
[Languages]
[Languages.en]
weight = 10
title = "In English"
languageName = "English"
contentDir = "content/english"
[Languages.nn]
weight = 20
title = "På Norsk"
languageName = "Norsk"
contentDir = "content/norwegian"
```
The value of `contentDir` can be any valid path, even absolute path references. The only restriction is that the content dirs cannot overlap.
The content files will be assigned a language by
1. The placement: `content/norwegian/post/my-post.md` will be read as Norwegian content.
2. The filename: `content/english/post/my-post.nn.md` will be read as Norwegian even if it lives in the English content folder.
The content directories will be merged into a big virtual filesystem with one simple rule: The most specific language file will win.
This means that if both `content/norwegian/post/my-post.md` and `content/english/post/my-post.nn.md` exists, they will be considered duplicates and the version inside `content/norwegian` will win.
Note that translations will be automatically assigned by Hugo by the content file's relative placement, so `content/norwegian/post/my-post.md` will be a translation of `content/english/post/my-post.md`.
If this does not work for you, you can connect the translations together by setting a `translationKey` in the content files' front matter.
Fixes #4523
Fixes #4552
Fixes #4553
This fixes some issues with language params handling by separating params from configuration values per language.
This means that you can now do this:
```toml
[languages]
[languages.en]
languageName = "English"
weight = 1
title = "My Cool Site"
[languages.en.params]
myParam = "Hi!"
```
This is not a breaking change, but the above is a less suprising way of configuring custom params.
It also fixes some hard-to-debug corner-cases in multilingual sites.
Fixes #4356
Fixes #4352
The gain, given the "real sites benchmark" below, is obvious:
```
benchmark old ns/op new ns/op delta
BenchmarkHugo-4 14497594101 13084156335 -9.75%
benchmark old allocs new allocs delta
BenchmarkHugo-4 57404335 48282002 -15.89%
benchmark old bytes new bytes delta
BenchmarkHugo-4 9933505624 9721984424 -2.13%
```
Fixes #2495
