Add dial support for sim800l component

[spilin]

Description: Dial support for sim800l component

Related issue (if applicable): fixes

Pull request in esphome-docs with documentation (if applicable): esphome/esphome-docs#esphome/esphome-docs#1027

Checklist:

• [x ] The code change is tested and works locally.
• [ x] Tests have been added to verify that the new code works (under tests/ folder).

If user exposed functionality or configuration variables are added/changed:

• [ x] Documentation added/updated in esphome-docs.

[probot-esphome]

Hey there @glmnet, mind taking a look at this pull request as its been labeled with an integration (sim800l) you are listed as a codeowner for? Thanks!
_{^{(message by CodeOwnersMention)}}

[glmnet]

Thanks!