Removed CI for Emacs 26.3 and 27.2

Added GitHub Actions CI badge. Remove Travis CI badge.

Added one more example on how to configure the mode line.

Create LICENSE

Added GPL 2.0 license file.

#21 Added test if bm-repository-file was not pointing to a writable f…

…ile.

#17 Fixed off-by-one with line numbers.

Added Melpa badge.