CI: install "lxml[html_clean]" for breadability

.github/workflows/run-tests.yml

@@ -59,7 +59,7 @@ jobs:
           python -m pip install --upgrade pip wheel setuptools
           pip install .
           # https://stackoverflow.com/a/69439779/2988107
-          pip install --upgrade numpy tinysegmenter jieba konlpy hebrew_tokenizer "tweepy<4.0.0" greek-stemmer-pos
+          pip install --upgrade numpy tinysegmenter jieba konlpy hebrew_tokenizer "tweepy<4.0.0" greek-stemmer-pos "lxml[html_clean]"
           python -c "import nltk; nltk.download('punkt')"
           pip install --upgrade pytest codecov pytest-cov