Add markup for automatic locale conversions

A lot of time is wasted, with the flow of conversation derailed, in online international chatting when asking for and receiving clarified local times, costs, distances, etc. Also, a lot of servers are used to announce events at certain times, and either need to supply a decent subset of conversions to popular time zones, or the users will all have to do so themselves.

It would be great if we were able to easily include automatically-localizable information in chat, such as time, temperature, distance, money, etc., and have it display on other people's screens in the locale format their system is set to use.

I'm not going to try to dictate the format of the markup, but for the sake of examples, I'll use one I've arbitrarily concocted and leave it to the Discord programmers to choose one that might be better. That said, here are some examples:

• .us types: It's %70F% here.
  .au reads: It's 70°F [21.1°C] here.
  .us reads: It's 70°F here.
  
  
• .nl types: It costs %100euro% here.
  .uk reads: It costs €100 [£89.07 today] here
  .nl reads: It costs €100 here
  
  
• .uk types: It starts at %0730bst%.
  .nz reads: It starts at 07:30 BST [18:30 CHAST].
  .uk reads: It starts at 07:30 BST.
  
  (It might be useful to allow a date as well, to allow future times to accommodate a change in daylight savings time in the interim, e.g. "%201905250730bst%". If the year is omitted, it should be assumed to be the this year or the next, depending on whether the datestamp would be in the past. It also might be nice to offer a "%now%" macro.)

Note that the original value should always be displayed, and any converted value should be called out by a difference in formatting, e.g. boldface and/or color, so there is never any confusion about what was seen vs. what was intended, in the rare case where the conversion might go wrong.

A potential alternative would be to either make the original value clickable or hoverable (or both) to see the conversion, rather than displaying it inline. You'd need to make it obvious that it's there, either with a style or maybe an accompanying icon/emoji.

And, even better, you could elect to automatically detect certain obvious things, like currency or distance, and offer a conversion even without the user formatting it specially. For instance:

• .ca user types: It costs $100 here.
  client submits: It costs %100cdn% here.
  
  
• anyone types: I drove 100km to get here.
  client submits: I drove %100km% to get here.

This could be toggled with an "Auto/Ask/Never" option, kinda like the auto-convert-to-emoji option, preferably defaulting to "Ask".

Also allow the user to deliberately avoid an automatic conversion by escaping the unit, e.g. "It costs \$100 here" or "I drove 100\km to get here" or the entire line, as done for other markup.

Okay, I think that's enough proposing. I bet there are other good things to convert locale-to-locale with this, and probably a few more macros like my proposed "%now%" time value, but I think you get what I'm on about. The nice thing about this is that it could start simple and grow incrementally, e.g. just do distance conversions to start, since those should be super-simple, then add time, then currency, and so on.

Fingers crossed! :)