FAQ/TODO/KNOWN_BUGS: convert to markdown

- convert to markdown
- auto-generate the TOCs on the website, remove them from the docs
- cleanups
- spellchecked
- updated links

Closes #19875

docs/Makefile.am

@@ -93,7 +93,7 @@ EXTRA_DIST =                                    \
  EARLY-RELEASE.md                               \
  ECH.md                                         \
  EXPERIMENTAL.md                                \
- FAQ                                            \
+ FAQ.md                                         \
  FEATURES.md                                    \
  GOVERNANCE.md                                  \
  HELP-US.md                                     \
@@ -108,7 +108,7 @@ EXTRA_DIST =                                    \
  INSTALL.md                                     \
  INTERNALS.md                                   \
  IPFS.md                                        \
- KNOWN_BUGS                                     \
+ KNOWN_BUGS.md                                  \
  KNOWN_RISKS.md                                 \
  MAIL-ETIQUETTE.md                              \
  MANUAL.md                                      \
@@ -121,7 +121,8 @@ EXTRA_DIST =                                    \
  SPONSORS.md                                    \
  SSL-PROBLEMS.md                                \
  SSLCERTS.md                                    \
- THANKS TODO                                    \
+ THANKS                                         \
+ TODO.md                                        \
  TheArtOfHttpScripting.md                       \
  URL-SYNTAX.md                                  \
  VERSIONS.md                                    \