Create dataset loader for Leipzig Corpora Collection

[SamuelCahyawijaya]

Dataloader name: leipzig_corpora/leipzig_corpora.py
DataCatalogue: http://seacrowd.github.io/seacrowd-catalogue/card.html?leipzig_copora

Dataset	leipzig_copora
Description	This is a collection of corpora in different languages, all built by randomly selecting sentences from web and newspaper sources. Each language has its own directory containing .txt files that list the words and sentences in the corpus, map words or sentences to their sources, and show the cooccurrence of words. The 2017 Community version of the collection contains text material crawled from different websites and contains data for 20 SEA languages.
Subsets	-
Languages	ban, bjn, bew, bcl, mya, ceb, hil, ind, khm, lao, zsm, min, pam, pag, ksw, tgl, tha, vie, war, jav, mad
Tasks	Language Modeling
License	Creative Commons Attribution 4.0 (cc-by-4.0)
Homepage	https://wortschatz.uni-leipzig.de/en/download
HF URL	-
Paper URL	http://www.lrec-conf.org/proceedings/lrec2012/pdf/327_Paper.pdf

[TysonYu]

#self-assign

[github-actions]

Hi @, may I know if you are still working on this issue? Please let @holylovenia @SamuelCahyawijaya @sabilmakbar know if you need any help.

[holylovenia]

Not sure why this wasn't linked to the PR. I already linked it now.