Add plan to tech stack section

docs/programming/web/tech-stack/plan.md

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+title = 'Plan for this section'
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+
+# Plan for this section
+
+List the various problem domains:
+
+e.g.
+
+- UX design
+- Theming
+- Search
+- Databases
+- Content management
+- Authentication and authorisation
+- Webserver config
+- Server administration
+- Containerisation
+- Version control
+
+For each problem domain, list skills and experience.