Add help message in case of bad --beacon-type configuration

[nalepae]

✅     validator 0x875fc22c proposed block at head at epoch 238032 - slot 7617038 ✅ - 🔑 32035 keys watched
✅     validator 0xb2da1ce0 proposed block at head at epoch 238032 - slot 7617039 ✅ - 🔑 32035 keys watched
❓     Missed attestations detection diabled for epoch 238031.
❓     You can ignore this message if the watcher just started less than one epoch ago. Otherwise, please check that you used the correct `--beacon-type` option (currently set to `other`).
❓     Use `--help` for more details.
✅     validator 0x8659ab70 proposed block at head at epoch 238032 - slot 7617040 ✅ - 🔑 32035 keys watched
👤 Our validator 0x803028d6, 0x804e28e0, 0x804eeee5, 0x8051ab55, 0x8075bbc4 and 228 more had not ideal rewards on head  at epoch 238030 (0.74%)
✅     validator 0xa8f44816 proposed block at head at epoch 238032 - slot 7617041 ✅ - 🔑 32035 keys watched
✅     validator 0xa29ad72e proposed block at head at epoch 238032 - slot 7617042 ✅ - 🔑 32035 keys watched
✅     validator 0xacf8e5ff proposed block at head at epoch 238032 - slot 7617043 ✅ - 🔑 32035 keys watched

[codecov]

Codecov Report

Merging #86 (aea73a3) into main (7f3e774) will not change coverage.
Report is 1 commits behind head on main.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##              main       #86   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           17        17           
  Lines          964       966    +2     
=========================================
+ Hits           964       966    +2     

Files	Coverage Δ
eth_validator_watcher/beacon.py	100.00% <100.00%> (ø)
eth_validator_watcher/entrypoint.py	100.00% <ø> (ø)
eth_validator_watcher/missed_attestations.py	100.00% <ø> (ø)
eth_validator_watcher/slashed_validators.py	100.00% <ø> (ø)
eth_validator_watcher/suboptimal_attestations.py	100.00% <ø> (ø)

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