Update to other messaging apps comparisons charts

[ghost]

• Mentioning those that are outdated/unmaintained and that those will be removed in next releases
• Adding https://github.com/bkil/secuchart which is a maintained project
• Adding disclaimer that we do not necessarily endorse their opinions
• Removed spaces between list items (and we should consider doing that on the whole guide)

[nopeitsnothing]

What happened to "Outdated, or unmaintained, or abandoned resources scheduled for removal from our guide in next release"?