Docker: Python 3.10 and Alpine 3.15 (#5443)

* Docker: Python 3.10 and Alpine 3.15

Author: oittaa

CONTRIBUTORS.txt

@@ -587,3 +587,5 @@ contributors:
 
 * Allan Chandler (allanc65): contributor
   - Fixed issue 5452, false positive missing-param-doc for multi-line Google-style params
+
+* Eero Vuojolahti: contributor

Dockerfile

@@ -1,4 +1,4 @@
-FROM python:3.9.0-alpine3.12
+FROM python:3.10.0-alpine3.15
 
 COPY ./ /tmp/build
 WORKDIR /tmp/build