Fix spelling errors

Lua API.html

@@ -3070,10 +3070,10 @@ on DF world events.</p>
 <p>Is called when projectile hits something.</p>
 </li>
 <li><p class="first"><tt class="docutils literal">onWorkshopFillSidebarMenu(workshop,callnative)</tt></p>
-<p>Is called when viewing a workshop in 'q' mode, to populate reactions, usefull for custom viewscreens for shops.</p>
+<p>Is called when viewing a workshop in 'q' mode, to populate reactions, useful for custom viewscreens for shops.</p>
 </li>
 <li><p class="first"><tt class="docutils literal">postWorkshopFillSidebarMenu(workshop)</tt></p>
-<p>Is called after calling (or not) native fillSidebarMenu(). Usefull for job button
+<p>Is called after calling (or not) native fillSidebarMenu(). Useful for job button
 tweaking (e.g. adding custom reactions)</p>
 </li>
 </ol>
@@ -3113,7 +3113,7 @@ b.onReactionComplete.one=function(reaction,unit,in_items,in_reag,out_items,call_
   call_native.value=false
 end
 </pre>
-<p>Granade example:</p>
+<p>Grenade example:</p>
 <pre class="literal-block">
 b=require &quot;plugins.eventful&quot;
 b.onProjItemCheckImpact.one=function(projectile)

Lua API.rst

@@ -2993,11 +2993,11 @@ List of events
 
 7. ``onWorkshopFillSidebarMenu(workshop,callnative)``
 
-   Is called when viewing a workshop in 'q' mode, to populate reactions, usefull for custom viewscreens for shops.
+   Is called when viewing a workshop in 'q' mode, to populate reactions, useful for custom viewscreens for shops.
 
 8. ``postWorkshopFillSidebarMenu(workshop)``
 
-   Is called after calling (or not) native fillSidebarMenu(). Usefull for job button
+   Is called after calling (or not) native fillSidebarMenu(). Useful for job button
    tweaking (e.g. adding custom reactions)
 
 Functions
@@ -3036,7 +3036,7 @@ Reaction complete example::
     call_native.value=false
   end
 
-Granade example::
+Grenade example::
 
   b=require "plugins.eventful"
   b.onProjItemCheckImpact.one=function(projectile)