Fix dead links for docs and add simple test for sourcelinks

Author: BarkingBad

docs/docs/contributing/getting-started.md

@@ -95,6 +95,6 @@ Before contributing to Dotty, we invite you to consult the
 Community
 -------------
 The main development discussion channels are:
-- [github.com/lampepfl/dotty/discussions](github.com/lampepfl/dotty/discussions)
-- [contributors.scala-lang.org](contributors.scala-lang.org)
-- [gitter.im/scala/contributors](gitter.im/scala/contributors)
+- [github.com/lampepfl/dotty/discussions](https://github.com/lampepfl/dotty/discussions)
+- [contributors.scala-lang.org](https://contributors.scala-lang.org)
+- [gitter.im/scala/contributors](https://gitter.im/scala/contributors)

docs/docs/internals/syntax.md

@@ -126,7 +126,7 @@ type      val       var       while     with      yield
 as  derives  end  extension  infix  inline  opaque  open  transparent  using  |  *  +  -
 ```
 
-See the [separate section on soft keywords](./soft-modifier.md) for additional
+See the [separate section on soft keywords](../reference/soft-modifier.md) for additional
 details on where a soft keyword is recognized.
 
 ## Context-free Syntax

project/Build.scala

@@ -1349,7 +1349,8 @@ object Build {
             "-comment-syntax", "wiki",
             "-siteroot", "docs",
             s"-source-links:docs=github://lampepfl/dotty/master#docs",
-            "-doc-root-content", docRootFile.toString
+            "-doc-root-content", docRootFile.toString,
+            "-Ydocument-synthetic-types"
           )
         ))
       }.evaluated,

scaladoc/test-source-links/dotty/tools/scaladoc/source-links/RemoteLinksTest.scala

@@ -29,6 +29,10 @@ class RemoteLinksTest:
   def scala3SourceLink =
     assertTrue(mtslAll.find((k, _) => k == "PolyFunction").isDefined) // source link to Scala3 stdlib class
 
+  @Test
+  def tastySourceLink =
+    assertTrue(mtslAll.find((k, _) => k == "TastyBuffer").isDefined) // source link to Scala3 tasty class
+
   @Test
   def runTest =
     assertTrue(mtslAll.nonEmpty)