docs: Fix link and mention Dfs and Bfs as special case in examples (#816)

I just noticed that the link for the example `Using algorithms on
graphs` in the docs does not work properly because there was a typo.

While at it, I also added a sentence about `Dfs` and `Bfs` not being
found in the algo module and instead in visit.
Similarly, I added links to the docstring of the `Topo` struct which was
referring to other functions/algs without linking to them.

Author: RaoulLuque

src/lib.rs

@@ -169,7 +169,7 @@ module documentation lists the available shorthand types.
 
 * [Creating an undirected graph and manipulating nodes and edges](#creating-an-undirected-graph-and-manipulating-nodes-and-edges)
 * [Differences of stable and non-stable graphs in index management](#differences-of-stable-and-non-stable-graphs-in-index-management)
-* [Using algorithms on graphs](#usign-algorithms-on-graphs)
+* [Using algorithms on graphs](#using-algorithms-on-graphs)
 * [Associating data with nodes and edges and transmuting the type of the data](#associating-data-with-nodes-and-edges-and-transmuting-the-type-of-the-data)
 * [Exporting graphs to DOT format](#exporting-graphs-to-dot-format)
 
@@ -280,8 +280,9 @@ Petgraph provides not only data structures for modeling graphs, but also a wide
 that can be applied to them. For example, given a graph, one can compute shortest paths,
 minimum spanning trees, or even compute the maximal cliques of a graph.
 
-Generally, algorithms are found in the [`algo`] module. All of them should include an example of
-how to use them. For example, to compute the minimum spanning tree of a graph, one can use the
+Generally, algorithms are found in the [`algo`] module, except for algorithms like
+depth-/breadth-first-search, which can be found in the [visit] module. All of them should include
+an example of how to use them. For example, to compute the minimum spanning tree of a graph, one can use the
 [`min_spanning_tree`](algo/min_spanning_tree/fn.min_spanning_tree.html) function.
 
 ```

src/visit/traversal.rs

@@ -311,8 +311,9 @@ where
 /// A topological order traversal for a graph.
 ///
 /// **Note** that `Topo` only visits nodes that are not part of cycles,
-/// i.e. nodes in a true DAG. Use other visitors like `DfsPostOrder` or
-/// algorithms like kosaraju_scc to handle graphs with possible cycles.
+/// i.e. nodes in a true DAG. Use other visitors like [`DfsPostOrder`] or
+/// algorithms like [`kosaraju_scc`][crate::algo::kosaraju_scc] to handle
+/// graphs with possible cycles.
 #[derive(Clone)]
 pub struct Topo<N, VM> {
     tovisit: Vec<N>,