feat: Implement customizable request timeout.

[Junkern]

What does this do / why do we need it?

People keep opening issues when the HTTP request times out. The timeout was 2 seconds. Now increased to 10 seconds and implemented the possibility to change the timeout value via environment variable.

[coveralls]

Pull Request Test Coverage Report for Build 2992988589

• 8 of 13 (61.54%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.04%) to 61.894%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
internal/app/install.go	2	3	66.67%
internal/app/app.go	6	10	60.0%

Totals
Change from base Build 2978210420:	-0.04%
Covered Lines:	281
Relevant Lines:	454

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 2992952971

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 7 of 12 (58.33%) changed or added relevant lines in 2 files are covered.
• 13 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.04%) to 61.894%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
internal/app/install.go	2	3	66.67%
internal/app/app.go	5	9	55.56%

Files with Coverage Reduction	New Missed Lines	%
internal/app/app.go	13	84.21%

Totals
Change from base Build 2978210420:	-0.04%
Covered Lines:	281
Relevant Lines:	454

---

💛 - Coveralls