Pull request as discussed

[luffah]

Hello as discussed by mail, here is my pull request. Before putting my code on git i verified some functionalities and had a function to manage CR, to have a standard Return key behavior when the cursor is in the middle of the line.
I updated the readme, plugin/zim and ftdetect/zim (in order to limit keybind to a zim buffer). Too, i changed a little the behavior of header keybind (titles h1 to h5): i changed the shortcut to not interfere with highlight, and i replaced the with a short dialog, for 2 reasons :

• counts wasn't working with my new function for defining title format.
• the way it works with counts demanded the user to be fully aware of how to use the shortcut -> therefore, to add a heading title 5, the procedure become wt5 instead of 5wh Hoping these change are acceptable in the same version (0). Best regards. -- luffah

[luffah]

This pull request has bugs on added functionality for adding bullet on CR . I've done the correction and made other change to find and jump between zim files. I think it will be simpler to up a version and announce this version to support navigation in zim Notebooks.