Typo fixes for welcome tour

[tripleee]

I would have created a pull request if I could find the related resources, but they don't seem to be in the Github repository.

The welcome tour is a nice feature, but it contains some typos etc which should probably be fixed.

s/add yours shortcuts/add your shortcuts/
s/and changed it, if/and change it if/

s/use the one/use the ones/
s/created your own/create your own/
s/will be appended/will be appended to/
s/you current list/your current list/

s%upload/donwload%upload / download%
s/some plugin's/some of the plugin's/

The example shortcuts have a typo in "I'm coming".

[tripleee]

I don't know why I didn't find the source the first time I looked. I have prepared a PR now.