book: add wiki links to the title page and install page (#3017)

Co-authored-by: amitbeka <--->

book/src/install.md

@@ -76,8 +76,13 @@ hx --health
 For more information on the information displayed in the healthcheck results refer to [Healthcheck](https://github.com/helix-editor/helix/wiki/Healthcheck).
 
 
-## Building tree-sitter grammars
+### Building tree-sitter grammars
 
 Tree-sitter grammars must be fetched and compiled if not pre-packaged.
 Fetch grammars with `hx --grammar fetch` (requires `git`) and compile them
 with `hx --grammar build` (requires a C++ compiler).
+
+### Installing language servers
+
+Language servers can optionally be installed if you want their features (auto-complete, diagnostics etc.).
+Follow the [instructions on the wiki page](https://github.com/helix-editor/helix/wiki/How-to-install-the-default-language-servers) to add your language servers of choice.

book/src/title-page.md

@@ -6,10 +6,12 @@ Docs for bleeding edge master can be found at
 See the [usage] section for a quick overview of the editor, [keymap]
 section for all available keybindings and the [configuration] section
 for defining custom keybindings, setting themes, etc.
+For everything else (e.g., how to install supported language servers), see the [Helix Wiki].
 
 Refer the [FAQ] for common questions.
 
 [FAQ]: https://github.com/helix-editor/helix/wiki/FAQ
 [usage]: ./usage.md
 [keymap]: ./keymap.md
 [configuration]: ./configuration.md
+[Helix Wiki]: https://github.com/helix-editor/helix/wiki