Add readme, update workflows

.gitea/workflows/latex.yml

@@ -1,6 +1,8 @@
 name: Create and publish container
 on:
-  push
+  push:
+    paths:
+      - latex/**
 jobs:
   build_container:
     runs_on: ubuntu-latest

README.md

@@ -0,0 +1,2 @@
+# Docker build files
+This repository contains various docker build files