Revert "Removed lxml dependency - not necessary after blog plugin rewrite"

This reverts commit 0986c3a039.

Dockerfile

@@ -47,12 +47,16 @@ RUN \
     git \
     git-fast-import \
     jpeg-dev \
+    libxml2 \
+    libxslt \
     openssh \
     zlib-dev \
 && \
   apk add --no-cache --virtual .build \
     gcc \
     libffi-dev \
+    libxml2-dev \
+    libxslt-dev \
     musl-dev \
 && \
   pip install --no-cache-dir --upgrade pip \

requirements.txt

@@ -29,6 +29,7 @@ pymdown-extensions>=9.9.1
 # Requirements for plugins
 babel>=2.10.3
 colorama>=0.4
+lxml>=4.6
 paginate>=0.5.6
 readtime>=2.0
 regex>=2022.4.24