You should always use the correct spelling and punctuation for the target language. From there define the correct language hinting in the meta tags on your page. Also if you are concerned about common misspellings you can also reference those in the meta tags in the header.

Modern browsers such as Google interpret misspellings and based on context will offer up results in the correct spelling. Meaning if you are at Google.al and type "keng", depending on context Google will know you probably meant "këngë".

eg, using English:

<meta http-equiv="content-language" content="en" />

<meta http-equiv="language" content="en" />

<meta name="description" content="brief description text that might have alternate spellings" />

<meta name="keywords" content="list of keywords including correctly and incorrectly spelled variants, with and without diacritics" />

Mixing spellings in and out of tags/cross tags as suggested in a comment to the OP can actually dilute your content and risks being identified as misleading. Don't do that.