Spelling corrections, user guides for apps

See merge request funkwhale/funkwhale!608

#662: Resolve "Add contexts to translatable strings"

See merge request funkwhale/funkwhale!612

#662: Resolve "Add contexts to translatable strings"

See merge request funkwhale/funkwhale!610

#662: Resolve "Add contexts to translatable strings"

See merge request funkwhale/funkwhale!609

#662: Resolve "Add contexts to translatable strings"

See merge request funkwhale/funkwhale!607

Minor rewording

@eliotberriot: Is there a reason why you used :v-context instead of
:translate-context?

Minor rewording

#662: Resolve "Add contexts to translatable strings"

See merge request funkwhale/funkwhale!605