Add ability to create ssh-keys and provide it to github and gitea

Here we start to have some delicate secrets in the code. Therefore I
need a vault for ansible. This vault contains the tokens to upload
ssh-keys to github and my lovely gitea server.

Note, that this change also adds a `requirements.yml`, this is necessary
because I use the paramater "api_url" of the github_key resource which
was only added in v11, but the debian ansible was shippped with an older
collection.

README.adoc

@@ -22,6 +22,13 @@ sudo apt install ansible git
 brew install ansible git
 ----
 
+=== password.txt
+To execute the playbook we need a password for the vault.
+This password has to be stored in a `password.txt` containing exactly one line with only the password as content.
+
+[NOTE]
+Use a secure password and keep it in a password-manager.
+
 == Setup
 Make sure to configure the local environment:
 This is done by copying `global_vars/localhost/local.config.yml.tpl` to `global_vars/localhost/local.config.yml` and adjust it to the local conditions.
@@ -41,5 +48,7 @@ After the configuration the setup is very simple:
 ----
 git clone git@gitea.nehrke.info:nemoinho/dev-machine.git ~/Development/nemoinho/dev-machine
 cd $_
+# make sure that we're on the latest requirements
+ansible-galaxy install -r requirements.yml --upgrade
 ansible-playbook main.yml
 ----