[Doc] Use absolute path when installing functions or using localrun

[lhotari]

Motivation

Absolute paths should be passed to pulsar-admin when creating functions/sinks/sources or when using localrun.
This should be explicitly mentioned in the documentation.

Additional context

Relative paths with pulsar-admin have never worked because of https://github.com/apache/pulsar/blob/50121e7f7be541f45bb6dc976f51e30658b1cb8d/bin/pulsar-admin#L26

[david-streamlio]

Looks good overall, just a few minor suggestions regarding the use of $PWD, and the exclusion of classname for NAR files.

[david-streamlio]

Is $PWD a safe assumption as to the proper location of the artifact, or should we use a more explicit nomenclature such as path/to/examples/api-examples.jar ?

[lhotari]

I think $PWD gives a good hint that it's an absolute path. At least I have found it useful with pulsar-admin when I have the files in the current directory and I want to reference the files with an absolute path. I guess there are also other ways. Perhaps it could be explained to the user that $PWD is the current working directory. They will also find out if they try it or google it. :)
In this particular case, the original /examples/api-examples.jar doesn't seem to make much sense. That's why I added the $PWD prefix.

[lhotari]

The /path/to/file.jar type of examples have the problem that for the user, it's really a lot of extra steps to find out the absolute path for the file arguments. That's why I prefer $PWD/file.jar since it's simple and if someone doesn't already know it, they have the chance to learn it.

$PWD is for a unix shell, but the examples are already assuming a unix shell since the syntax is all unix like.

[david-streamlio]

LGTM