When adding tags, search for part of the tag

[asitemade4u]

Tags are great but one has to be careful not to create duplicate keywords. Sometimes, when one has a lot of tags, it is very easy to forget the ones available for tagging. That may cause duplicates by recreating a tag that has already been created, but under a slightly different form -- eg. tree when nat_tree has already been defined. Currently, Linkding searches only on tag begins with, when tagging entries. It would be better to search on tag contains > in our example above, a search on tree would have yielded nat_treeand I would not have been tempted to create a duplicate tag.