In #526 I accidentally lost some of my edits trying to selectively
stage lines with typo fixes, while deleting hunks that were only
whitespace changes. In hopes nobody else falls into this trap, I ran
the following command to find all the files to edit, and apply emacs's
delete-trailing-whitespace function to each file.
```sh
find * -type f -print0 | xargs -0 -P$(nproc) -n1 -I{} sh -c 'if file -b "{}" | grep -qFi text; then emacs -batch "{}" -f delete-trailing-whitespace -f save-buffer; fi'
```
Note: `git add -u` will add only known paths to the stage (index),
even if `tidy.sh` exists in the git work directory.
* Updated Opera and Flycast core and image names
* Updated Opera and Flycast BIOSes
* Fixed minor grammar in most core pages
* Corrected a few remnant messy links from the relative link cleanup
* Updated some outdated links and info, notably for Mesen
* Added VBA-M and Mesen-S to GB/GBC "Related Cores" sections
* Updated Beetle core names
* First round of updates to the Softpatching guide
Latency page added https://github.com/libretro/docs/issues/261
index links re-ordered, RetroArch prefix removed from list so it's more clean
new links like Lakka, Facebook, Steam Group etc. added
Implemented enchancement stated in issue #502.
With different netplay information segments added the netplay user guide information was split up and reorganized a little bit.
netplay-multiple-controllers.md is new content.
Other comments related to issue #502:
Detailed configuration explanation should be put in the control tool tips available inside retroarch.
