New feature: Build script inheritance

[nightroman]

New feature: Build script inheritance
(Consider it as preview in v5.14.x)

Build script parameters Extends with ValidateScript attributes tell to
dot-source scripts and replace Extends with inherited base parameters.

Documentation / examples

• Invoke-Build/Tasks/Extends at main · nightroman/Invoke-Build
• Building FarNet Showcase · nightroman/Invoke-Build Wiki

[nightroman]

Support common parameters on "Extends" · Issue #228 · nightroman/Invoke-Build

• v5.14.3

[nightroman]

Support task prefixes on "Extends" · Issue #229 · nightroman/Invoke-Build

• v5.14.4

[nightroman]

Add new build variable $BuildRoots · Issue #231 · nightroman/Invoke-Build

• v5.14.8

[nightroman]

"Extends" prefixes -- current rules · Issue #232 · nightroman/Invoke-Build

• v5.14.10