chore: make yuzu REUSE compliant

[REUSE] is a specification that aims at making file copyright
information consistent, so that it can be both human and machine
readable. It basically requires that all files have a header containing
copyright and licensing information. When this isn't possible, like
when dealing with binary assets, generated files or embedded third-party
dependencies, it is permitted to insert copyright information in the
`.reuse/dep5` file.

Oh, and it also requires that all the licenses used in the project are
present in the `LICENSES` folder, that's why the diff is so huge.
This can be done automatically with `reuse download --all`.

The `reuse` tool also contains a handy subcommand that analyzes the
project and tells whether or not the project is (still) compliant,
`reuse lint`.

Following REUSE has a few advantages over the current approach:

- Copyright information is easy to access for users / downstream
- Files like `dist/license.md` do not need to exist anymore, as
  `.reuse/dep5` is used instead
- `reuse lint` makes it easy to ensure that copyright information of
  files like binary assets / images is always accurate and up to date

To add copyright information of files that didn't have it I looked up
who committed what and when, for each file. As yuzu contributors do not
have to sign a CLA or similar I couldn't assume that copyright ownership
was of the "yuzu Emulator Project", so I used the name and/or email of
the commit author instead.

[REUSE]: https://reuse.software

Follow-up to 01cf05bc75

src/yuzu/aboutdialog.ui

@@ -127,7 +127,7 @@ p, li { white-space: pre-wrap; }
        <item>
         <widget class="QLabel" name="labelLinks">
          <property name="text">
-          <string>&lt;html&gt;&lt;head/&gt;&lt;body&gt;&lt;p&gt;&lt;a href=&quot;https://yuzu-emu.org/&quot;&gt;&lt;span style=&quot; text-decoration: underline; color:#039be5;&quot;&gt;Website&lt;/span&gt;&lt;/a&gt; | &lt;a href=&quot;https://github.com/yuzu-emu&quot;&gt;&lt;span style=&quot; text-decoration: underline; color:#039be5;&quot;&gt;Source Code&lt;/span&gt;&lt;/a&gt; | &lt;a href=&quot;https://github.com/yuzu-emu/yuzu/graphs/contributors&quot;&gt;&lt;span style=&quot; text-decoration: underline; color:#039be5;&quot;&gt;Contributors&lt;/span&gt;&lt;/a&gt; | &lt;a href=&quot;https://github.com/yuzu-emu/yuzu/blob/master/license.txt&quot;&gt;&lt;span style=&quot; text-decoration: underline; color:#039be5;&quot;&gt;License&lt;/span&gt;&lt;/a&gt;&lt;/p&gt;&lt;/body&gt;&lt;/html&gt;</string>
+          <string>&lt;html&gt;&lt;head/&gt;&lt;body&gt;&lt;p&gt;&lt;a href=&quot;https://yuzu-emu.org/&quot;&gt;&lt;span style=&quot; text-decoration: underline; color:#039be5;&quot;&gt;Website&lt;/span&gt;&lt;/a&gt; | &lt;a href=&quot;https://github.com/yuzu-emu&quot;&gt;&lt;span style=&quot; text-decoration: underline; color:#039be5;&quot;&gt;Source Code&lt;/span&gt;&lt;/a&gt; | &lt;a href=&quot;https://github.com/yuzu-emu/yuzu/graphs/contributors&quot;&gt;&lt;span style=&quot; text-decoration: underline; color:#039be5;&quot;&gt;Contributors&lt;/span&gt;&lt;/a&gt; | &lt;a href=&quot;https://github.com/yuzu-emu/yuzu/blob/master/LICENSE.txt&quot;&gt;&lt;span style=&quot; text-decoration: underline; color:#039be5;&quot;&gt;License&lt;/span&gt;&lt;/a&gt;&lt;/p&gt;&lt;/body&gt;&lt;/html&gt;</string>
          </property>
          <property name="openExternalLinks">
           <bool>true</bool>