Add FlexibleType support for scaladoc #148

Job	Run time
scala-library-nonbootstrapped	57s
scala3-library-nonbootstrapped	1m 4s
scala3-library-bootstrapped	3m 56s
test-tasty-core-nonbootstrapped	1m 5s
tasty-core-nonbootstrapped	1m 1s
scala3-sbt-bridge-nonbootstrapped	3m 10s
test-scala3-sbt-bridge-bootstrapped	5m 39s
scala3-compiler-bootstrapped	5m 57s
test-tasty-core-bootstrapped	4m 3s
tasty-core-bootstrapped	3m 58s
test-scala3-sbt-bridge-nonbootstrapped	3m 49s
scala3-compiler-nonbootstrapped	3m 40s
scala3-sbt-bridge-bootstrapped	5m 49s
scala-library-bootstrapped	4m 4s
	48m 12s

Provide feedback