Previously only one translation file per locale could be loaded.
Now the user can specify multiple files per locale, and the translations
from each of these files will be merged together by message id.
The merging is on a first-wins approach. So if to you have three files
to be merged:
```
['a.xlf', 'b.xmb', 'c.json']
```
Then any message from `a.xlf` will be used rather than a message from `b.xmb`
or `c.json` and so on. In practice this means that you should put the files
in order of most important first, with "fallback" translations later.
PR Close#36792
The `:` char is used as a metadata marker in `$localize` messages.
If this char appears in the metadata it must be escaped, as `\:`.
Previously, although the `:` char was being escaped, the TS AST
being generated was not correct and so it was being output double
escaped, which meant that it appeared in the rendered message.
As of TS 3.6.2 the "raw" string can be specified when creating tagged
template AST nodes, so it is possible to correct this.
PR Close#33820
Pete Bacon Darwin
George Kalpakas
Filipe Silva