Add Drone CI config, remove Gitlab CI config

.drone.yml

+---
+kind: pipeline
+type: docker
+name: build
+
+steps:
+- name: docker  
+  image: plugins/docker
+  settings:
+    username:
+      from_secret: registry_user
+    password:
+      from_secret: registry_password
+    repo: fat0troll/tdlib-golangci
+    auto_tag: true

Dockerfile

-FROM lab.wtfteam.pro:4567/containers/golangci-lint AS build
+FROM golangci/golangci-lint:v1.19.1 AS build
 
 LABEL maintainer="vladimir@hodakov.me"
 
-COPY --from=lab.wtfteam.pro:4567/containers/tdlib /usr/local/include/td /usr/local/include/td
-COPY --from=lab.wtfteam.pro:4567/containers/tdlib /usr/local/lib/libtd* /usr/local/lib/
+COPY --from=fat0troll/tdlib /usr/local/include/td /usr/local/include/td
+COPY --from=fat0troll/tdlib /usr/local/lib/libtd* /usr/local/lib/
 
-RUN apk update && apk add --no-cache git gcc libc-dev g++ make openssl-dev zlib-dev && rm -rf /var/cache/apk/*
+RUN apt-get update && apt-get -y install libssl-dev cmake zlib1g-dev g++
+RUN apt-get clean autoclean && apt-get autoremove --yes && rm -rf /var/lib/apt/lists/*

ci/set_docker_tag.sh

-#!/usr/bin/env bash
-
-if [[ $CI_BUILD_REF_NAME == "master" ]]; then
-    export DOCKER_TAG=latest;
-else
-    export DOCKER_TAG="${CI_BUILD_REF_NAME}";
-fi