docs: add tool request template

Author: rjaegers

.github/ISSUE_TEMPLATE/tool_request.md

@@ -0,0 +1,20 @@
+---
+name: Tool request
+about: Request to include an additional tool
+title: 'Request to include <tool>'
+labels: enhancement
+assignees: ''
+
+---
+
+**What tool would you like to include**
+A clear and concise description of the tool you would want to include. Ex. I want to add tool x that does [...]
+
+**What is the use-case for the inclusion**
+Describe why the proposed tool should be added. Please note that project specific tools
+should be added to a derived container instead of adding them to amp-devcontainer.
+
+**What is the estimated size impact**
+Describe what the estimated (or absolute) size impact of the inclusion would be on the final
+image [size](https://en.wikipedia.org/wiki/Byte#Multiple-byte_units).
+Ex. The container image size will increase with 5 MiB.