Ignore a couple of files

The `host.json` file should no longer be necessary as -- according to
https://learn.microsoft.com/en-us/azure/azure-functions/functions-host-json
-- it is only applicable to Azure Functions runtimes up to v2.x, and we
already use v4.x. But hey, it's tradition to ignore the `host.json`
file.

Also, ignore the `local.settings.json` file. This is more relevant: when
testing the Azure Function locally, this file will contain the secrets,
among other things, and should therefore never be committed.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Author: dscho

.gitignore

@@ -0,0 +1,2 @@
+/host.json
+/local.settings.json