Allow customization of link text

[legalnonsense]

This is the second time I've ever tried a pull request, so bear with me if I didn't do this correctly.

I added some features I needed for this package to be useful to me:

1. allow user to customize the link text using a string with replacement strings. See org-media-note-link-format. This also requires org-media-note--link-formatter;
2. custom option to move cursor to before the link text after it is inserted;
3. custom option to add a prefix string to link text that is not part of the link;
4. interactive function to insert a link and pause the video (to be able to take a note during the pause).

No idea if you like any of these features or the code, but wanted to share in case they were useful.

[yuchen-lea]

Oh! I'm soooooooo happy to receive your PR. I just start writing elisp package and this is my first PR received. Your features are greatly welcome. It may takes some time to merge since there're a lot to learn from your code ;)

[legalnonsense]

It is a very useful package and if I can be of any help I am happy to. Tried to use emms to do something similar and it was buggy. This just seems to work. Thank you for sharing!

[yuchen-lea]

I've made some modifications based on your pr:

1. 89c527d I change some default value of the variable you defined, in order to keep consistent with the previous behavior. Maybe you need set your own preference in config.
2. 7604424 org-media-note-insert-link-and-pause is removed and use variable org-media-note-pause-after-insert-link instead. When non-nil, the media file will pause after insert link both for manually calling org-media-note-insert-link, and auto insering links in a list (org-media-note-item). Also, you can toggle the variable by org-media-note-toggle-pause-after-insertion, which can be accessed from hydra menu directly. I think it's a more general way, although I'm not sure whether this fits your need.