Add suppport for decimal plurals (Android cs/fr/lt/sk are missing "many" in plurals)

### Describe the issue

Android's _lint_ tool is complaining about missing "many" entries in plural strings for "cs" (Czech), "fr" (French) , "lt" (Lithuanian), and "sk" (Slovak). The Weblate interface does not offer "many" as an option for those languages/strings. For example:

https://gitlab.com/grote/fdroidclient/-/jobs/2351872888
```
^
/builds/grote/fdroidclient/app/src/main/res/values-cs/strings.xml:396: Error: For locale "cs" (Czech) the following quantities should also be defined: many [MissingQuantity]

^
/builds/grote/fdroidclient/app/src/main/res/values-cs/strings.xml:401: Error: For locale "cs" (Czech) the following quantities should also be defined: many [MissingQuantity]

^
/builds/grote/fdroidclient/app/src/main/res/values-lt/strings.xml:406: Error: For locale "lt" (Lithuanian) the following quantities should also be defined: many [MissingQuantity]

^
/builds/grote/fdroidclient/app/src/main/res/values-lt/strings.xml:501: Error: For locale "lt" (Lithuanian) the following quantities should also be defined: many [MissingQuantity]

^
Explanation for issues of type "MissingQuantity":
Different languages have different rules for grammatical agreement with
quantity. In English, for example, the quantity 1 is a special case. We
write "1 book", but for any other quantity we'd write "n books". This
distinction between singular and plural is very common, but other languages
make finer distinctions.
This lint check looks at each translation of a and makes sure that
all the quantity strings considered by the given language are provided by
this translation.
For example, an English translation must provide a string for
quantity="one". Similarly, a Czech translation must provide a string for
quantity="few".
https://developer.android.com/guide/topics/resources/string-resource.html#Plurals
```

This is related to #1550. This site seems to say it is a matter of conversion between the CLDR and gettext representation schemes for plurals:
https://github.com/miracle2k/android2po#plurals-support

### I already tried

- [X] I've read and searched [the documentation](https://docs.weblate.org/).
- [X] I've searched for similar issues in this repository.

### Steps to reproduce the behavior

These are some of the strings:
* https://hosted.weblate.org/translate/f-droid/f-droid/lt/?offset=1&q=button_view_all_apps_in_category&sort_by=-priority%2Cposition&checksum=
* https://hosted.weblate.org/translate/f-droid/f-droid/cs/?offset=1&q=details_last_update_months&sort_by=-priority%2Cposition&checksum=

### Expected behavior

Weblate should support the "many" field for Android strings.xml for cs/fr/lt/sk languages.

### Screenshots

_No response_

### Exception traceback

_No response_

### How do you run Weblate?

weblate.org service

### Weblate versions

_No response_

### Weblate deploy checks

_No response_

### Additional context

_No response_