TASK: Fix typos in documentation and some strings

[benno5020]

Hello!

First of all, thank you for your work!
Just like in neos/neos-development-collection#5846 I fixed typos in this repository too.

Upgrade instructions

n/a

Review instructions

I split my fixes into separate commits so changes in code (comments) and documentation are easily discernible. Note that c6d0157 changes actual strings in the code.

Checklist

• Code follows the PSR-2 coding style
• [~] Tests have been created, run and adjusted as needed
• The PR is created against the lowest maintained branch
• Reviewer - PR Title is brief but complete and starts with FEATURE|TASK|BUGFIX
• Reviewer - The first section explains the change briefly for change-logs
• Reviewer - Breaking Changes are marked with !!! and have upgrade-instructions

[kdambekalns]

Thanks a lot.