Add github issue and pull request templates

I do not understand why github requires adding this crap to source code
repositories themselves, instead of making them part of the repository
configuration. Remove CONTRIBUTING.md to compensate for github crap
accumulating.

.github/ISSUE_TEMPLATE

@@ -0,0 +1,14 @@
+### mpv version and platform
+
+If you're not using git master or the latest release, update.
+
+### Expected behavior
+
+### Actual behavior
+
+### Reproduction steps
+
+### Log files
+
+Make a log file made with -v or --log-file=output.txt, paste it to sprunge.us,
+and replace this text with a link to it.

.github/PULL_REQUEST_TEMPLATE

@@ -0,0 +1,7 @@
+Ideally, you shouldn't need enter any text here, and your commit messages should
+explain your changes sufficiently (especially why they are needed). Read
+https://github.com/mpv-player/mpv/blob/master/DOCS/contribute.md for coding
+style and development conventions. Remove this text block, but if you haven't
+agreed to it before, leave the following sentence in place:
+
+I agree that my changes can be relicensed to LGPL 2.1 or later.

CONTRIBUTING.md

@@ -1,32 +0,0 @@
-Reporting bugs
-==============
-
-- State your platform and mpv version.
-- Make sure you're actually using the latest mpv release. Linux distributions
-  in particular love redistributing ancient and unmaintained mpv releases.
-- Attach a log file made with ``-v`` or ``--log-file=output.txt``.
-- Avoid attaching text files packed in archive files (zip/rar/...), unless
-  explicitly asked so. There are better means, such as using http://sprunge.us
-- If you think this is file specific, upload a sample file and link it.
-- Don't report multiple unrelated/barely related bugs in one issue.
-- If you don't get a reply after days, be sure to post a new message to the
-  issue - it could have been overlooked or forgotten.
-- Read: https://mpv.io/bug-reports/
-
-Asking questions
-================
-
-Preferably, asking questions should be done via IRC (#mpv on irc.freenode.net),
-but asking questions by opening a github issue is also barely tolerated.
-
-When asking on IRC (#mpv on irc.freenode.net), don't ask to ask, just state
-your problem. Stay long enough until someone gets a chance to reply. Sometimes
-it can take hours.
-
-Sending patches
-===============
-
-See: https://github.com/mpv-player/mpv/blob/master/DOCS/contribute.md
-
-In particular, be aware that all changes to GPL code must come with the
-implicit agreement that they might be LGPLv2.1+ relicensed at a later point.