chore: fix PyYAML version

docs.Dockerfile

@@ -1,4 +1,4 @@
-FROM alpine
+FROM alpine:3.14
 
 ENV PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/root/.local/bin
 

requirements.txt

@@ -2,3 +2,38 @@ mkdocs==0.17.5
 pymdown-extensions==4.12
 mkdocs-bootswatch==0.5.0
 mkdocs-material==2.9.4
+
+appdirs==1.4.4
+CacheControl==0.12.6
+certifi==2020.12.5
+chardet==4.0.0
+click==8.1.3
+colorama==0.4.4
+contextlib2==0.6.0
+distlib==0.3.1
+distro==1.5.0
+html5lib==1.1
+idna==3.2
+importlib-metadata==4.12.0
+Jinja2==3.1.2
+livereload==2.6.3
+lockfile==0.12.2
+Markdown==3.3.7
+MarkupSafe==2.1.1
+msgpack==1.0.2
+ordered-set==4.0.2
+packaging==20.9
+pep517==0.10.0
+progress==1.5
+Pygments==2.12.0
+pymdown-extensions==4.12
+pyparsing==2.4.7
+PyYAML==6.0.1
+requests==2.25.1
+retrying==1.3.3
+six==1.15.0
+toml==0.10.2
+tornado==4.5.3
+urllib3==1.26.5
+webencodings==0.5.1
+zipp==3.8.1