v1.19.0 - Free cocompletions and constituents of regular categories

In this release, most of the work went into #340, adding a cocomplete category without equalizers and deciding all of its properties. In this context, free cocompletions of locally small categories have been studied in general. Moreover, I have started to extract the pieces of the property of being regular; namely by adding the properties of having kernel pairs and of having coequalizers of kernel pairs. For a full list of changes, see the list of PRs and their descriptions below.

Features 🧪

• Combinations script by @ScriptRaccoon in #347
• Design improvements by @ScriptRaccoon in #348

Database 🔋

• Add natural numbers objects without parameters by @ScriptRaccoon in #339
• Add kernel pairs and cokernel pairs by @ScriptRaccoon in #342
• Coequalizers of kernel pairs by @ScriptRaccoon in #343
• Add concretizable categories by @ScriptRaccoon in #346
• Add an example of a cocomplete category without equalizers by @ScriptRaccoon in #340

Refactor 🧹

• Content pages for reusable content only by @ScriptRaccoon in #338
• Support proof environments by @ScriptRaccoon in #341

Full Changelog ⚙️

v1.18.0...v1.19.0