Fix broken known language servers link, add entry point mention

Author: krassowski

CONTRIBUTING.md

@@ -325,15 +325,16 @@ python scripts/lint.py
 While language servers can be configured by the user using a simple JSON or Python [configuration file](./Configuring.ipynb#language_servers),
 it is preferable to provide users with an option that does not require manual configuration. The language server specifications (specs)
 wrap the configuration (as would be defined by the user) into a Python class or function that can be either:
-
 - distributed using PyPI/conda-forge and made conveniently available to users for `pip install` and/or `conda install`
 - contributed to the collection of built-in specs of jupyter-lsp by opening a PR (preferable for popular language servers, say >100 users)
 
+In either case the detection of available specifications uses Python `entry_points` (see the `[options.entry_points]` section in jupyter-lsp [setup.cfg]).
+
 > If an advanced user installs, locates, and configures, their own language server it will always win vs an auto-configured one.
 
 #### Writing a spec
 
-A spec is a Python callable (a function or class with `__call__` method) that accepts a single argument, the
+A spec is a Python callable (a function, or a class with `__call__` method) that accepts a single argument, the
 `LanguageServerManager` instance, and returns a dictionary of the form:
 
 ```python
@@ -351,7 +352,6 @@ For details on the dictionary contents, see the [schema][] definition and [built
 Basic concepts (meaning of the `argv` and `languages` arguments) are also explained in the [configuration files](./Configuring.ipynb#language_servers) documentation.
 
 When contributing a specification we recommend to make use of the helper classes and other [utilities][] that take care of the common use-cases:
-
 - `ShellSpec` helps to create specs for servers that can be started from command-line
 - `PythonModuleSpec` is useful for servers which are Python modules
 - `NodeModuleSpec` will take care of finding Node.js modules
@@ -366,6 +366,7 @@ The spec should only be advertised if the command _could actually_ be run:
 otherwise an empty dictionary (`{}`) should be returned.
 
 [built-in specs]: https://github.com/krassowski/jupyterlab-lsp/tree/master/python_packages/jupyter_lsp/jupyter_lsp/specs
+[setup.cfg]: https://github.com/krassowski/jupyterlab-lsp/blob/master/python_packages/jupyter_lsp/setup.cfg
 [schema]: https://github.com/krassowski/jupyterlab-lsp/blob/master/python_packages/jupyter_lsp/jupyter_lsp/schema/schema.json
 [utilities]: https://github.com/krassowski/jupyterlab-lsp/blob/master/python_packages/jupyter_lsp/jupyter_lsp/specs/utils.py
 

docs/Configuring.ipynb

@@ -144,7 +144,7 @@
     "> default: `True`\n",
     "\n",
     "If `True`, `jupyter-lsp` will look for all\n",
-    "[known language servers](#installing-language-servers). User-configured\n",
+    "[known language servers](./Language%20Servers.ipynb). User-configured\n",
     "`language_servers` of the same implementation will be preferred over\n",
     "`autodetect`ed ones."
    ]
@@ -199,13 +199,12 @@
    "source": [
     "### Python `entry_points`\n",
     "\n",
-    "`pip`-installable packages in the same environment as the Jupyter `notebook`\n",
-    "server can be automatically detected as providing\n",
-    "[language_servers](#language_servers). These are a little more involved, but\n",
-    "also more powerful: see more in [Contributing](Contributing.ipynb#Specs).\n",
-    "Servers configured this way are loaded _before_ those defined in\n",
-    "[configuration files](#Configuration-Files), so that a user can fine-tune their\n",
-    "available servers."
+    "`pip`-installable packages in the same environment as the Jupyter server can be\n",
+    "automatically detected as providing [language_servers](#language_servers). These\n",
+    "are a little more involved, but also more powerful: see more in\n",
+    "[Contributing](Contributing.ipynb#Specs). Servers configured this way are loaded\n",
+    "_before_ those defined in [configuration files](#Configuration-Files), so that a\n",
+    "user can fine-tune their available servers."
    ]
   },
   {