fix: add Slovak Ĺ/ĺ (L with acute) to the char map

[spokodev]

Ĺ (U+0139) and ĺ (U+013A) are part of the Slovak alphabet (e.g. stĺp, hĺbka) but are missing from the char map. Because the default remove regex relies on \w (ASCII-only), unmapped non-ASCII letters are stripped entirely:

slugify('stĺp')   // 'stp'   (expected 'stlp')
slugify('Ĺúbime') // 'ubime' (expected 'Lubime')

Slovak support was added in #42 (Ľ/ľ, Ŕ/ŕ) but the L-acute pair was overlooked (reported in #94). Add Ĺ→L, ĺ→l, matching the existing ľ→l, ł→l, ļ→l. Closes #94.