ci: Add dependabot configuration for monthly updates #305

Job	Run time
Code quality (ty and ruff)	37s
Link correctness	7s
Build documentation	1m 0s
Tests (py3.11, ubuntu-latest, float32, full)	1m 24s
Tests (py3.10, ubuntu-latest, float32, full)	1m 16s
Tests (py3.14, ubuntu-latest, float32, full)	1m 14s
Tests (py3.12, ubuntu-latest, float32, full)	1m 23s
Tests (py3.13, ubuntu-latest, float32, full)	1m 21s
Tests (py3.14, macOS-latest, float32, full)	48s
Tests (py3.10.0, ubuntu-latest, float32, full, lower_bounds)	1m 7s
Tests (py3.14, ubuntu-latest, float32, none)	1m 14s
Tests (py3.14, ubuntu-latest, float64, full)	1m 11s
Tests (py3.14, windows-latest, float32, full)	2m 17s
	14m 59s

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