Support portable-ascii 1.x on 8.0.x

[MoamenEltouny]

Allows voku/portable-ascii 1.x on the 8.0.x line (^1.6.1 || ^2.0), for release as 8.0.4.

Laravel 7 and 8 require portable-ascii 1.x, while every 8.x line of this package required 2.x, so pharaonic/php-slugify could not be installed next to them. This blocks pharaonic/laravel-sluggable 7.x and 8.x.

Same output with 1.x and 2.x

Comparing every BMP letter (49,638) across every portable-ascii language, 1.x and 2.x differ on only a few letters:

• Generic table: Persian پ (b instead of p) and the Cyrillic ё ъ ы э ю я. 1.x also turns э into e', which split words: Мэр gave me-r.
• Language maps: fa (پ, ج), uk (16 letters, already covered by the Ukrainian override) and latin (4 letters).

When 1.x is installed, PortableAsciiTransliterator replaces those letters with the 2.x result before calling portable-ascii. Generic replacements are skipped where the language has its own entry, so ru keeps yolka. The table lives in src/Resources/portable-ascii-1.php. Detection is a single cached check (پ → b only on 1.x), and nothing changes when 2.x is installed.

After the change, the same comparison gives 0 differences, and the test suite (including the locale corpus) passes on both 1.6.1 and 2.1.1. The CI lowest dependency jobs now run on 1.6.1.

Note on portable-ascii 2.1

portable-ascii 2.1 has a fast path for strings up to 64 bytes that gives different results from its full path on longer strings when no locale is set (ёлка + 40 letters → elka, + 60 letters → iolka). This change matches the per-letter results, which is also what the corpus expects. With 1.x, the result no longer depends on the string length.

The CHANGELOG has an 8.0.4 entry, and the installation docs list both versions.