Add manual track addition to hls endpoint

[codecov[bot]]

Codecov Report

Merging #328 (f8ab02c) into master (ec9aa2d) will increase coverage by 0.13%. The diff coverage is 0.00%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #328 +/- ## ========================================== + Coverage 53.80% 53.93% +0.13% ========================================== Files 41 41 Lines 2061 2056 -5 ========================================== Hits 1109 1109 + Misses 952 947 -5 ``` | [Files](https://app.codecov.io/gh/jellyfish-dev/membrane_rtc_engine/pull/328?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=jellyfish-dev) | Coverage Δ | | |---|---|---| | [hls/lib/hls\_endpoint.ex](https://app.codecov.io/gh/jellyfish-dev/membrane_rtc_engine/pull/328?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=jellyfish-dev#diff-aGxzL2xpYi9obHNfZW5kcG9pbnQuZXg=) | `50.45% <ø> (+0.03%)` | :arrow_up: | | [engine/lib/membrane\_rtc\_engine/engine.ex](https://app.codecov.io/gh/jellyfish-dev/membrane_rtc_engine/pull/328?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=jellyfish-dev#diff-ZW5naW5lL2xpYi9tZW1icmFuZV9ydGNfZW5naW5lL2VuZ2luZS5leA==) | `81.22% <0.00%> (-0.95%)` | :arrow_down: | ... and [3 files with indirect coverage changes](https://app.codecov.io/gh/jellyfish-dev/membrane_rtc_engine/pull/328/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=jellyfish-dev) ------ [Continue to review full report in Codecov by Sentry](https://app.codecov.io/gh/jellyfish-dev/membrane_rtc_engine/pull/328?src=pr&el=continue&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=jellyfish-dev). > **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=jellyfish-dev) > `Δ = absolute (impact)`, `ø = not affected`, `? = missing data` > Powered by [Codecov](https://app.codecov.io/gh/jellyfish-dev/membrane_rtc_engine/pull/328?src=pr&el=footer&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=jellyfish-dev). Last update [ec9aa2d...f8ab02c](https://app.codecov.io/gh/jellyfish-dev/membrane_rtc_engine/pull/328?src=pr&el=lastupdated&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=jellyfish-dev). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=jellyfish-dev).