Enable DCM rule double-literal-format.
More details
[here](https://dcm.dev/docs/rules/common/double-literal-format/). This
both forbids trailing zeroes and mandates leading zeroes.
If we would prefer a different style (e.g. prefer no leading zero
instead), just lmk :)
I was playing around with the rule avoid-global-state
While I don't think we should enable it, because we do have several totally legitimate cases of what the rule considers global state, it did help me find any current cases where the things just should be final constants.
So this PR will mark semantically final variables as final (or const) proper, exclusively on examples (no violations on actual src code are legit).
