Update current stable versions automatically

[jaxxzer]

Hard coding these adds maintenance overhead and makes them likely to stale as software is updated. https://github.com/bluerobotics/ardusub-gitbook/pull/152

[ES-Alexander]

Case in point, we're now up to companion 0.0.26 and the installation docs still say 0.0.22 (which is what they were when this issue was raised).

Any progress on this? Perhaps it's worth making a quick script that just knows which files refer to the version number in them, and then when a new version is about to be released that script can be called to replace all instances of the old version number in those files with the new one.