Add counter documentation/examples. Tweak counter triggers/actions in automod.

Rename change_counter automod action to add_to_counter,
add set_counter action, rename counter trigger to counter_trigger.

backend/src/plugins/Automod/actions/addToCounter.ts

@@ -0,0 +1,22 @@
+import * as t from "io-ts";
+import { automodAction } from "../helpers";
+import { CountersPlugin } from "../../Counters/CountersPlugin";
+
+export const AddToCounterAction = automodAction({
+  configType: t.type({
+    counter: t.string,
+    amount: t.number,
+  }),
+
+  defaultConfig: {},
+
+  async apply({ pluginData, contexts, actionConfig, matchResult }) {
+    const countersPlugin = pluginData.getPlugin(CountersPlugin);
+    countersPlugin.changeCounterValue(
+      actionConfig.counter,
+      contexts[0].message?.channel_id || null,
+      contexts[0].user?.id || null,
+      actionConfig.amount,
+    );
+  },
+});