docs: migrate Docker instructions to relative bind mount

[MikeMcC399]

Issue

The README > Run using Docker command example

docker run -v ${PWD}:/tmp:ro --rm -i ghcr.io/tcort/markdown-link-check:stable /tmp/README.md

uses PWD (Print Working Directory). The syntax ${PWD} can now be replaced by a simpler one using relative paths.

Relative paths

The Docker documentation for docker container run (with alias docker run) describes the option Mount volume (-v) using relative paths:

As of Docker Engine version 23, you can use relative paths on the host.

docker run -v ./content:/content -w /content -i -t ubuntu pwd

• Docker Engine 23.0.0 was released on Feb 1, 2023. The current version is
• Docker Engine 27.3.1 released on Sep 20, 2024.

Change

Use the relative path . syntax instead of ${PWD}:

docker run -v .:/tmp:ro --rm -i ghcr.io/tcort/markdown-link-check:stable /tmp/README.md

Verification

Under Ubuntu 24.04.1 LTS

git clone https://github.com/tcort/markdown-link-check
cd markdown-link-check
docker run -v .:/tmp:ro --rm -i ghcr.io/tcort/markdown-link-check:stable /tmp/README.md

Confirm that markdown-link-check runs successfully.