Update mkdocs dependencies and pin macro plugin

images/mkdocs/Dockerfile

@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-FROM alpine:3.10
+FROM alpine:3.12
 
 RUN apk add --no-cache \
   bash \

images/mkdocs/requirements.txt

@@ -1,5 +1,5 @@
-mkdocs-material~=5.2.3
+mkdocs-material~=5.5.14
 mkdocs~=1.1.2
-pymdown-extensions==7.1
-pygments~=2.6.1
-mkdocs-macros-plugin~=0.4.9
+pymdown-extensions==8.0
+pygments~=2.7.1
+mkdocs-macros-plugin==0.4.9