Doc: Add more hyperlinks within the included documentation (#11288)

Co-authored-by: Niels Martin Hansen <nielsm@indvikleren.dk>

CONTRIBUTING.md

@@ -182,6 +182,16 @@ There is no single source for OpenTTD development docs. It's a complex project w
 A good entry point is [Development](https://wiki.openttd.org/en/Development/) on the OpenTTD wiki; this provides links to wiki documentation and other sources.
 
 The GitHub repo also includes some non-comprehensive documentation in [/docs](./docs).
+These include:
+- When to [change other languages and when not to](./docs/eints.md).
+- The [savegame format](./docs/savegame_format.md).
+- The [release process](./docs/releasing_openttd.md).
+- Some [notes on the link graph algorithm](./docs/linkgraph.md).
+- The [network game coordinator](./docs/game_coordinator.md).
+- How to use [the admin port for network games](./docs/admin_network.md), also useful for multiplayer server hosts.
+- The [performance metrics and logging features](./docs/logging_and_performance_metrics.md), also useful for add-on developers.
+- How [symbol server and analysis works](./docs/symbol_server.md).
+- And several miscellaneous files detailing internal data structures and graphics measurements and palettes.
 
 You may also want the guide to [compiling OpenTTD](./COMPILING.md).
 

COPYING.md

@@ -1,5 +1,5 @@
 This is the license which applies to OpenTTD with the exception of some
-3rd party modules. See [./README.md](./README.md) for details
+3rd party modules. See [our readme](./README.md) for details
 
 GNU General Public License
 ==========================

README.md

@@ -11,9 +11,10 @@
     - 1.6) [OpenTTD directories](#16-openttd-directories)
     - 1.7) [Compiling OpenTTD](#17-compiling-openttd)
 - 2.0) [Contact and community](#20-contact-and-community)
-    - 2.1) [Contributing to OpenTTD](#21-contributing-to-openttd)
-    - 2.2) [Reporting bugs](#22-reporting-bugs)
-    - 2.3) [Translating](#23-translating)
+    - 2.1) [Multiplayer games](#21-multiplayer-games)
+    - 2.2) [Contributing to OpenTTD](#22-contributing-to-openttd)
+    - 2.3) [Reporting bugs](#23-reporting-bugs)
+    - 2.4) [Translating](#24-translating)
 - 3.0) [Licensing](#30-licensing)
 - 4.0) [Credits](#40-credits)
 
@@ -144,12 +145,19 @@ If you want to compile OpenTTD from source, instructions can be found in [COMPIL
 - the OpenTTD wiki has a [page listing OpenTTD communities](https://wiki.openttd.org/en/Community/Community) including some in languages other than English
 
 
-### 2.1) Contributing to OpenTTD
+### 2.1) Multiplayer games
+
+You can play OpenTTD with others, either cooperatively or competitively.
+
+See the [multiplayer documentation](./docs/multiplayer.md) for more details.
+
+
+### 2.2) Contributing to OpenTTD
 
 We welcome contributors to OpenTTD.  More information for contributors can be found in [CONTRIBUTING.md](./CONTRIBUTING.md)
 
 
-### 2.2) Reporting bugs
+### 2.3) Reporting bugs
 
 Good bug reports are very helpful.  We have a [guide to reporting bugs](./CONTRIBUTING.md#bug-reports) to help with this.
 
@@ -157,7 +165,7 @@ Desyncs in multiplayer are complex to debug and report (some software developmen
 Instructions can be found in [debugging and reporting desyncs](./docs/debugging_desyncs.md).
 
 
-### 2.3) Translating
+### 2.4) Translating
 
 OpenTTD is translated into many languages.  Translations are added and updated via the [online translation tool](https://translator.openttd.org).
 

docs/debugging_desyncs.md

@@ -53,4 +53,7 @@ Do NOT remove the dmp_cmds savegames of a desync you have reported until the
 desync has been fixed; if you, by accident, send us the wrong savegames we
 will not be able to reproduce the desync and thus will be unable to fix it.
 
+## More information
 
+You can find more theory on the causes and debugging of desyncs in the
+[desync documentation](./desync.md).

docs/multiplayer.md

@@ -193,6 +193,9 @@ If it is, and your server still isn't showing up, start OpenTTD with
 `-d net=4` as extra argument. This will show debug message related to the
 network, including communication to/from the Game Coordinator.
 
+See the [Game Coordinator documentation](./game_coordinator.md) for more
+technical information about the Game Coordinator service.
+
 ### My server warns a lot about getaddrinfo taking N seconds
 
 This could be a transient issue with your (local) DNS server, but if the