Fix typos in documentation

Fix typos spotted by T-A-R#8121 in the documentation.

docs/configuration.md

@@ -129,7 +129,7 @@ Defaults to "New Slave".
 
 ### slave.id
 
-Imutable numeric id of the slave which uniquely identifies this slave in
+Immutable numeric id of the slave which uniquely identifies this slave in
 the cluster.
 
 Defaults to a random 31 bit number.

packages/lib/README.md

@@ -5,4 +5,4 @@ This package contains functionality shared between master, slave, ctl
 and/or plugins of Clusterio.
 
 See [the Clusterio repository](https://github.com/clusterio/factorioClusterio)
-for more inforation on Clusterio.
+for more information on Clusterio.

plugins/statistics_exporter/README.md

@@ -2,7 +2,7 @@ Clusterio Statistics Exporter Plugin
 ====================================
 
 Plugin exporting item production, fluid production, kill count, entity
-build and poluttion statistics to the Prometheus integration to
+build and pollution statistics to the Prometheus integration to
 Clusterio.