Update event text to better reflect number involved, show keynote first.

[kattni]

This addresses a request from @freakboy3742 for the following:

• When there is only one team member involved in an event, use pronouns to refer to them in the involvement type section, instead of repeating their name.
• When there is a keynote, show it first.

It also modifies the following:

• Updates the conclusion grammar to use pronouns if the earlier text is using them.
• Fixes a link in the .authors.yml file.
• Fixes a spelling error in one of the events.

PR Checklist:

• All new features have been tested
• All new features have been documented
• I have read the CONTRIBUTING.md file
• I will abide by the code of conduct