Support yaml keywords in syntax highlighting and remove batch ones

[de-jcup]

The editor was initially created from copying batch-editor and make string replace search...

So some keywords from origin editor are currently highlighted. Must be removed and replaced with keywords relevant for Yaml:

[de-jcup]

Will do:

• yes
• no
• false
• true as special variables, see https://juliankniephoff.wordpress.com/2012/09/01/reserved-words-in-yaml-and-translating-booleans-in-rails/

and also

• %YAML
• %TAG as reservered (directive) word, see http://yaml.org/spec/1.2/spec.html#id2767222 and https://symfony.com/doc/current/components/yaml/yaml_format.html

[de-jcup]