Rules: git remote add instead of set-url if remote does not exist

Tests: Added test for git_remote_seturl_add

Rules: renamed new rule with a more appropriate name

README: added new rule

Style: Formatting

New rule: corrected test name

Developed tests

README.md

@@ -166,6 +166,7 @@ using the matched rule and runs it. Rules enabled by default are as follows:
 * `git_pull_clone` – clones instead of pulling when the repo does not exist;
 * `git_push` – adds `--set-upstream origin $branch` to previous failed `git push`;
 * `git_push_pull` – runs `git pull` when `push` was rejected;
+* `git_remote_seturl_add` – runs `git remote add` when `git remote set_url` on nonexistant remote;
 * `git_stash` – stashes you local modifications before rebasing or switching branch;
 * `git_two_dashes` – adds a missing dash to commands like `git commit -amend` or `git rebase -continue`;
 * `go_run` – appends `.go` extension when compiling/running Go programs;