Add `pagerank` example

[mtsokol]

Hi @hameerabbasi,

Here I share initial pagerank implementation (following scipy_pagerank).

A few comments:

• It's slower than scipy implementation.
• spdiag is still missing in finch-tensor, therefore I use SciPy diag to create it.

[github-actions[bot]]

Test Results

5 923 tests  ±0   5 891 :white_check_mark: ±0   9m 24s :stopwatch: -7s     1 suites ±0      32 :zzz: ±0      1 files   ±0       0 :x: ±0 

Results for commit b2e63af8. ± Comparison against base commit c12b29eb.

This pull request skips 2 and un-skips 2 tests.

``` sparse.numba_backend.tests.test_compressed ‑ test_reductions_float16[f4-None-sum-kwargs0] sparse.numba_backend.tests.test_coo ‑ test_reductions_float16[f8-None-sum-kwargs0] ``` ``` sparse.numba_backend.tests.test_compressed ‑ test_reductions_float16[i4-None-sum-kwargs0] sparse.numba_backend.tests.test_coo ‑ test_reductions_float16[i4-None-sum-kwargs0] ```

:recycle: This comment has been updated with latest results.