users can create channels in non-english languages

context

• as of !528 (merged) , users can create their own channels
• in 9d6cf506, @aguestuser somewhat overambitiously attempted to add support for localized welcome messages for newly created channels
• this was prematur (and subsequently reverted) since we don't currently expose to users any way to create original channel memberships in any languages other than english
• so... this MR exposes the ability to request channels in non-english languages, and notifies them in the language in which the channel was created

behavior

(stub!)

command discovery

WHEN a user issues REQUEST (in any language)

• THEN they will see the explanator text specified in #379 (closed) (implemented in !518 (merged)) explaining that issuing CHANNEL will create a new channel
• BUT THEN they will also see a listing of non-English variants of CHANNEL (in ES, FR, DE). The first variant will in the language they used to issue REQUEST (the others will be alphabetic)

WHEN a user visits the splash page

• THEN the Getting Started section will explain that users can use EN, FR, ES, or DE to request a new channel and list command variants in each language

channel creation / notifications

WHEN a user issues CHANNEL in a non-English language

• THEN the original memberships for that channel will all be created in that language
• AND THEN the original admins will all receive welcome messages and/or invites to the support channel in that language

open questions:

• should the REQUEST command response in fact always list all variants of the CHANNEL command? perhaps it would be cleaner simply to list the variant in the language that REQUEST was issued?

implementation:

• there is already code for localized welcome messages and support channel invites in this (now reverted) commit: 9d6cf506
• there are already non-English variants of the REQUEST and CHANNEL command in app/dispatcher/strings/commands/EN.js