code.dlang.org reliability update

[Sönke Ludwig]

As of yesterday, code.dlang.org now points to a more powerful dedicated 
server that can host the DUB registry without the danger of freezing due 
to excessive swapping - this is what happened on the 26th last month [1].

In addition to that, the server that previously hosted the registry is 
now used to run an official mirror, reachable at codemirror.dlang.org. 
This will be configured as a built-in fallback server starting with DMD 
2.091.0/DUB 1.12.0 and, at least in theory, will lead to an uptime of 
virtually 100%.

To make use of the mirror today, it is also possible to configure it in 
DUB's settings.json as a custom registry:

{
    "registryUrls": ["https://codemirror.dlang.org/"]
}

settings.json is found/needs to be created in %APPDATA%\dub\ on Windows 
and in ~/.dub/ on all other systems. The custom entry should be removed 
once DUB 1.12.0 is used, to avoid redundant requests in certain situations.


[1]: https://forum.dlang.org/thread/ontwwoxuhnoczcokacwm@forum.dlang.org