feat(docs): various improvements

- removing spaces at end of line
- fixing spelling and grammar mistakes
- making sure 'Vikunja' is spelled the same way everywhere
- prefer using editors word wrap instead of hardcoding word wrap in markdown (reason: different word wrap per editor & end of line space)
- add newline add end where missing
- remove double colon at end of headlines
- remove unnecessary indention
- make sure code blocks and headlines etc always have an empty line around

docs/content/doc/development/cron.md

@@ -12,9 +12,7 @@ menu:
 Cron jobs are tasks which run on a predefined schedule.
 Vikunja uses these through a light wrapper package around the excellent [github.com/robfig/cron](https://github.com/robfig/cron) package.
 
-The package exposes a `cron.Schedule` method with two arguments: The first one to define the schedule when the cron task 
-should run, and the second one with the actual function to run at the schedule.
-You would then create a new function to register your the actual cron task in your package.
+The package exposes a `cron.Schedule` method with two arguments: The first one to define the schedule when the cron task should run, and the second one with the actual function to run at the schedule. You would then create a new function to register your the actual cron task in your package.
 
 A basic function to register a cron task looks like this: