docs: clarify container label usage

[EDIflyer]

As discussed in #1318 - just to aid clarity for new users and also make docker-compose element clear.

[piksel]

You can make the examples tabbed, like on the start page like this:

watchtower/docs/index.md

Lines 47 to 65 in 30f36b3

	=== "docker run"
	```bash
	$ docker run -d \
	--name watchtower \
	-v /var/run/docker.sock:/var/run/docker.sock \
	containrrr/watchtower
	```
	=== "docker-compose.yml"
	```yaml
	version: "3"
	services:
	watchtower:
	image: containrrr/watchtower
	volumes:
	- /var/run/docker.sock:/var/run/docker.sock
	```

[codecov]

Codecov Report

Merging #1319 (d6f3749) into main (739f328) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #1319   +/-   ##
=======================================
  Coverage   63.82%   63.82%           
=======================================
  Files          23       23           
  Lines        1534     1534           
=======================================
  Hits          979      979           
  Misses        465      465           
  Partials       90       90           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 30f36b3...d6f3749. Read the comment docs.

[EDIflyer]

@piksel good suggestion - still getting my head round mkdocs - have tweaked to 3 tabs for the 2 scenarios, hopefully have got it right but obviously doesn't show up on Github's markdown interpreter!

[EDIflyer]

sorry had renamed my branches so they made more sense, didn't realise that would automatically close the PR!

[piksel]

Looks good overall, but I think the examples should be reduced a bit to make it clearer what is actually required.

[EDIflyer]

Looks good overall, but I think the examples should be reduced a bit to make it clearer what is actually required.

Thanks - all very sensible suggestions 👍