added some links to roadmap

docs/src/roadmap.md

@@ -2,14 +2,21 @@
 This page documents some planned work for RecurrentLayers.jl.
 Future work for this library includes additional cells such as:
 
- - Unitary recurrent neural networks
- - Linear recurrent neural networks
- - Quasi recurrent neural networks
+ - FastRNNs and FastGRUs (current focus) [arxiv](https://arxiv.org/abs/1901.02358)
+ - Unitary recurrent neural networks [arxiv](https://arxiv.org/abs/1611.00035)
+ - Modern recurrent neural networks such as [LRU](https://arxiv.org/abs/2303.06349) 
+   and [minLSTM/minGRU](https://arxiv.org/abs/2410.01201)
+ - Quasi recurrent neural networks [arxiv](https://arxiv.org/abs/1611.01576)
 
 Additionally, some cell-independent architectures are also planned,
 that expand the ability of recurrent architectures and could theoretically take
 any cell:
 
- - Clockwork rnns
- - Segment rnn
- - Fast-Slow rnns
+ - Clockwork rnns [arxiv](https://arxiv.org/abs/1402.3511)
+ - Phased rnns [arxiv](https://arxiv.org/abs/1610.09513)
+ - Segment rnn [arxiv](https://arxiv.org/abs/2308.11200)
+ - Fast-Slow rnns [arxiv](https://arxiv.org/abs/1705.08639)
+
+An implementation of these ideally would be,
+for example `FastSlow(RNNCell, input_size => hidden_size)`.
+More details on this soon!