Dependabot for libs bundled in Python guest

[crepererum]

What

Set up dependabot to auto-update the libraries that we bundle with our Python guest.

Why

Automatically get security fixes and other improvements.

How

This likely only makes sense after #102. Then point dependabot to

https://github.com/influxdata/datafusion-udf-wasm/blob/bd9e6670fee18f7629206b6828aa4fa9abbad6a8/guests/python/requirements.txt

similar to this config here:

datafusion-udf-wasm/.github/dependabot.yml

Lines 23 to 30 in bd9e667

	- package-ecosystem: "pip"
	directory: ".github/workflows"
	schedule:
	interval: "weekly"
	groups:
	github-deps:
	patterns:
	- "*"